An electrical connection box includes a case; a power supply circuit; and a branch circuit, wherein the branch circuit includes a detachable overcurrent protection element and branches from the power supply circuit; the case includes a case body, a cover detachably attached to the case body, and a cover sealing member having elasticity; the case body includes a first working hole and houses the power supply circuit and the branch circuit; the first working hole is formed at a position that allows the overcurrent protection element to face outward and is formed with external shape dimensions smaller than external shape dimensions of a ceiling plate; the cover is installed on the case body such that the first working hole is closed; and the cover sealing member is brought into close contact with a peripheral edge portion of the first working hole of the case body and the cover.