An electronic device is provided that includes a housing, a waterproof air-permeable membrane, a door, an air pressure gauge and a watertightness detector. The housing defines an opening and includes an air vent. The waterproof air-permeable membrane blocks off the air vent. The door is shiftably coupled to the housing and movable between a first position that uncovers the opening and a second position that covers the opening. The door and the housing form a watertight structure when the door is in the second position. The air pressure gauge is disposed inside the watertight structure. The watertightness detector is configured to determine whether the housing and the door have maintained a watertight state based on changes in the air pressure inside the watertight structure when the door moves from the first to the second position. The changes in the air pressure are measured by the air pressure gauge.