A portable electric power tool powered by a battery pack, which includes: a motor that operates the tool; the housing that houses the motor; at least one elastic member that is supported by the housing; and a battery pack holder supported by the elastic member. The battery pack holder is provided with an engaging portion that is detachably engaged with the case of the battery pack and connecting terminals that are electrically connected to the output terminals of the battery pack installed by the engaging portion. Thus, vibration of the battery pack is prevented even when the electric power tool vibrates.