An electronic device includes a first unit having an engaging target part and a second unit having a lock mechanism. The lock mechanism includes an operation member movable between a first position and a second position, an engagement part, and a drive mechanism that drives the engagement part. The drive mechanism includes a moving member causing the engagement part to be engaged with the engaging target part when the moving member is located at a first moving position and causing the engagement part to be disengaged from the engaging target part when the moving member is located at the second moving position. The lock mechanism has a holding mechanism holds the moving member at the second moving position when the operation member is moved to the second position, and releases of the moving member held at the second moving position when the first unit is attached to the second unit.