ELECTRICAL CONNECTION BOX

An electrical connection box (1) includes: a box main body (2) including a cylindrical sidewall (20) and a locking part (50); and a cover (3). The sidewall includes a first wall part (21) and a second wall part (22). The locking part includes a first locking part (51) and a second locking part (52). The cover (3) includes a first opposing wall (31), a first lock piece (61) disposed on the first opposing wall, a second opposing wall (32), and a second lock piece (62) disposed on the second opposing wall. The first opposing wall includes a first opposing part (31a) and a second opposing part (31b). The second opposing part is located closer to the second opposing wall side than the first opposing part is, and the first lock piece is located at an end part of the first opposing part close to the second opposing part.