The Diet, in a bid to encourage working women to have children, enacted legislation Wednesday requiring employers to provide child-care facilities and programs.
The move is part of efforts to reverse the declining birthrate amid the aging society.
The law requires local governments and private-sector employers with 300 or more workers to introduce child-care programs beginning in fiscal 2005.
The Health, Labor and Welfare Ministry said it plans to draw up a list of child-care programs that private-sector employers can use as a reference for their own programs.
The programs include targets for paternity and maternity leave, overtime exemptions for employees with small children and shortened work hours for staff with preschoolers.
Ministry officials said private-sector employers will have the discretion to decide their own child-care programs.
The law, expected to enter into force Monday, will expire in fiscal 2014.
The House of Councilors passed the bill early Wednesday afternoon. The legislation had already cleared the House of Representatives.