Document and Entity Information	12 Months Ended
	Jan. 30, 2013
Risk/Return:
Document Type	485BPOS
Document Period End Date	Sep. 30, 2012
Registrant Name	PUTNAM MONEY MARKET FUND
Central Index Key	0000081248
Amendment Flag	false
Document Creation Date	Jan. 28, 2013
Document Effective Date	Jan. 30, 2013
Prospectus Date	Jan. 30, 2013