This study investigated the effects of mothers' parenting stress and parenting style, child temperaments, supports from spouses and society on developments of both employed and unemployed mothers The participants are 583 employed mothers, 1,179 unemployed mothers, and their 1,762 early children. The average age of the children was 25 months old, which is the transitional period from sensorimotor stage to preoperational stage. The findings are as follows. First, language developmental levels of the employed mothers' child and spouses' supports were higher and parenting stress was lower than the unemployed mothers' controlling for monthly household income and parents' education levels. Second, the most significant variables that affected on employed mothers' and unemployed mothers' child development were child temperaments. Finally, employed mothers' parenting stress and styles mediated the relationships of child temperaments, spouses' supports, and social support with child language development. Findings were discussed regarding the effects of mothers' employment on child development in the transitional period from the sensorimotor stage to preoperational stage.