Abstract: A splashproof construction for a portable electronic device, comprising an electronic device main unit, and a battery pack to be mounted on the electronic device main unit, whereby one of either the electronic device main unit or the battery pack has a boundary surface formed along a combined surface and a peripheral edge and with a graded step with respect to the combined surface, and a guide rail provided adjacent to the boundary surface, and the other of either the electronic device main unit or the battery pack has a peripheral wall aligned with the boundary surface and a guide groove to be slidably engaged with the guide rail, or a bottom wall of the peripheral wall has a notch abutting on a lower surface of the graded step on the boundary surface, or a water-repellent sheet is provided at the bottom of the guide groove, or a seal plate made of a highly elastic material is provided either on an end surface of the battery pack abutted on the electronic device main unit at an end point of sliding when the