To provide a battery cooler which can heat and cool a battery module by a simple constitution.

A module assembly 3 is housed in a cabinet 2. A blast member 5 is installed opposing to the outer peripheral face of the cabinet 2. The blast member 5 is constituted to be switchable from: the cooling state of the cooling direction C which is the direction of air in the cabinet 2 toward the module assembly 3; and the heating state of the heating direction H which is the direction of air in the cabinet 2 toward the opposite direction to the cooling direction. An equipment box 6 is installed to house a DC/DC convertor to the downstream side of the direction of cooling C of the cabinet 2. The DC/DC convertor is an exothermic means to exotherm in operation.