A handheld electronic device includes a first body, a second body, a flexible electrical connector, and a protection cover. The second body is slidably stacked with the first body. The flexible electrical connector is electrically connected between the first body and the second body. The cover is slidably disposed between the first body and the second body. The cover is at an initial position when the first body and the second body are in a stacked state. The cover shields the flexible electrical connector exposed after the second body moves when the first body and the second body are in a spread state. As a result, the lifetime of the handheld electronic device can be prolonged. Additionally, the available region of the handheld electronic device in the spread state can be increased to provide higher design flexibility.