This research began from the interest in that how much effectiveness the Work-Family Balance policy has according to the position of female workers as women's participation in economic activity increases. Focus has been placed on maternity protection system, the most representative of the Work-Family Balance policy, and on Irregular Working Mothers. Therefore the range of maternity protection system was defined and the payroll, fund and the content of pay were analyzed. Concerning the range of the maternity protection system defined in this study, it was divided into the system that supports maternity protection directly and the system that supports it indirectly. The direct support system includes vacation support system, working hour regulation support system and cash support system(to employer), while the indirect support system includes the policy project that supports career-broken women by employment support system. Analysis showed that both vacation support system and working hour regulation support system confined the payroll to those whose insurable unit period of employment insurance is over 180 days. This system is impossible for Irregular Working Mothers, who are not insured for the employment insurance, to even make an approach. The cash support system(to employer) might also legalize Irregular Working Mothers as its support period is limited and the employment is decided according to employer. On the other hand, concerning the employment support system, though the indirect support of maternity protection system does not exclude Irregular Working Mothers from the payroll, the pattern of employable position is short-term contract of which the form of work or the status of employee is inadequate. Considering above result, this research suggested an alternative so that maternity protection system could be applied regardless of women's status of work.