To provide a battery jar capable of improving ruggedness without impairing the cooling function.

This battery jar includes a batter jar mainbody 6 for storing a power generation element having condensing function and being held at their ends by a constraining band 5, a plurality of radiating fins 11 arranged outside the battery jar mainbody 6 ranging from one constraining band 5 side to the other constraining band 5 side and recesses 12 formed between the radiating fins 11, wherein a curved face 13 curved in an arched shape in the protruded direction of the radiating fins 11 is formed in an area encircling the recess 12 in the battery jar mainbody 6.