A power source apparatus includes a power source module which is formed of a plurality of power source elements, a case which houses the power source module and a cooling liquid, a fan which is placed in the case in a state in which the fan is immersed in the cooling liquid together with the power source module, the fan forming a laminar flow of the cooling liquid, the laminar flow having a width at least substantially the same as a length of the power source element in a length direction of the power source element.