When a battery pack is mounted to a battery attachment part, the battery pack is slid in a horizontal direction (a direction substantially perpendicular to an upper-lower direction) with respect to the housing, e.g., along a long longitudinal direction of a battery-side rail part, such that tool-side rail parts of the battery attachment part are introduced into engaging recess portions of the battery pack. Thereby, the elastic members are fitted and compressed in the battery-side rail parts and the tool-side rail parts, so that the elastic members press upwards the battery-side rail part (e.g., the battery pack) and press downwards the tool-side rail parts (e.g., the housing). That is, the elastic members press the battery pack and the housing such that they come close to each other.