Objectives: The objectives of this study were to classify never-married types of adult men and women and explore factors related to these types. Never-married types were categorized into 4 types according to continuity and voluntariness: continuous voluntary type; changed voluntary type; continuous non-voluntary type; and changed non-voluntary type. Factors related to types of being single were examined in terms of socio-demographic factors, individual and psychological factors (self-esteem, depression), dating relationship factors (current relationship status), original family factors (parental conflict, relationship with parents, parents' demand for marriage), marriage related factors (division of roles after marriage), and occupation related factors (work values, employment instability). Method: As for research method, a survey was conducted with never-married adult men and women between the ages of 35 and 49 living in Seoul, Gyeonggi or Incheon areas. Of 300 copies of questionnaire distributed, data from 295 copies were processed using SPSS 24.0 program for multinomial logit analysis. Results: The study results showed that, of never-married men respondents, continuous voluntary type accounted for 20.5%; changed voluntary type 18.9%; continuous non-voluntary type 49.6%; and changed non-voluntary type 11.0%. It was found that the factors related to continuous non-voluntary type among never-married men are age, religion, average monthly income, while the factors related to changed voluntary type are religion, self-esteem, depression, and frequency and strength of parental conflict, while the factor related to changed non-voluntary type men was living with parents. Examining never-married women respondents, it was found that, continuous voluntary type accounted for 33.9%; changed non-voluntary type 19.6%; continuous non-voluntary type 22.6%; and changed voluntary type 23.8%. The factor related to continuous non-voluntary type among never-married women was parents' demand for marriage, while the factors related changed voluntary type were age, depression and strength of parental conflict. Also, the factors related to changed non-voluntary type of never-married women were age, religion, living with parents, depression and parents' demand for marriage. Conclusion: In conclusion, it was found that continuous non-voluntary type formed the largest group among never-married men, whereas continuous voluntary type was the majority in never-married women. Both never-married men and women chose to remain single when they are living with their parents and their parental conflict is intense. Parents' demand for marriage was related to women, but not to men.