A power storage device comprising: a battery (5, 5a, 5b, 5c, 5d); and a casing which accommodates the battery (5, 5a, 5b, 5c, 5d) and has a sealing structure, wherein the casing includes a first member accommodating the battery (5, 5a, 5b, 5c, 5d) and including a first opening and a second member covering the first opening, wherein the first and second members (7, 8) are joined to each other at a first joint portion provided at a peripheral edge of the first opening, wherein the first joint portion includes a first peripheral groove portion and a first reception port (16, 116) provided at one of the first and second members (7, 8), a first convex edge portion provided at the other thereof, a first claw portion provided on a side surface of the first convex edge portion, and a first adhesive layer disposed inside the first peripheral groove portion, wherein a front end of the first convex edge portion is disposed inside the first peripheral groove portion and is bonded to an inner wall of the first peripheral groove portion by the first adhesive layer, wherein the first claw portion is disposed inside the first reception port, wherein the first claw portion has a hook shape and engages with the first reception port by a snap-fit structure, and wherein the first adhesive layer bonds the front end of the first convex edge portion to the inner wall of the first peripheral groove portion in a state in which a side surface of the first claw portion opposite to the front end of the first convex edge portion is in contact with an inner wall of the first reception port opposite to a bottom of the first peripheral groove portion. a battery (5, 5a, 5b, 5c, 5d); and a casing which accommodates the battery (5, 5a, 5b, 5c, 5d) and has a sealing structure, wherein the casing includes a first member accommodating the battery (5, 5a, 5b, 5c, 5d) and including a first opening and a second member covering the first opening, wherein the first and second members (7, 8) are joined to each other at a first joint portion provided at a peripheral edge of the first opening, wherein the first joint portion includes a first peripheral groove portion and a first reception port (16, 116) provided at one of the first and second members (7, 8), a first convex edge portion provided at the other thereof, a first claw portion provided on a side surface of the first convex edge portion, and a first adhesive layer disposed inside the first peripheral groove portion, wherein a front end of the first convex edge portion is disposed inside the first peripheral groove portion and is bonded to an inner wall of the first peripheral groove portion by the first adhesive layer, wherein the first claw portion is disposed inside the first reception port, wherein the first claw portion has a hook shape and engages with the first reception port by a snap-fit structure, and wherein the first adhesive layer bonds the front end of the first convex edge portion to the inner wall of the first peripheral groove portion in a state in which a side surface of the first claw portion opposite to the front end of the first convex edge portion is in contact with an inner wall of the first reception port opposite to a bottom of the first peripheral groove portion.