To heighten handleability and to improve weight balance, by compacting a handle part in the cross direction, whereas, since a portable circular saw of a battery type has a constitution in which a battery pack is usually mounted on a handle rear part longitudinally so that its longitudinal direction is set along the cross direction, compaction in the cross direction is difficult.

Such a constitution is adopted that a battery pack 20 is mounted laterally so that its longitudinal direction L is set orthogonally to a machining progress direction, in the slid state in the lateral direction, with respect to a rear part of a handle part 11, and dismounted. Hereby, handleability thereof can be heightened by compacting a handle part tool, and further weight balance can be improved.