In a rotary electric device for a power working machine capable of being braked by a brake mechanism (B), a cover (C) having a bottomed cylindrical shape and covering a yoke (Y) of the device, includes: a cover cylindrical portion (Cc) concentrically surrounding an outer peripheral surface of a cylindrical portion of the yoke (Yc) with an annular clearance therebetween, and having an outer peripheral surface with which a brake shoe (Bs) is capable of being placed in pressure contact and a cover bottom wall portion (Cb) continuous to one end of the cover cylindrical portion (Cc), and connected to a bottom wall portion (Yb) of the yoke. A ventilation clearance (21) communicating with the annular clearance is formed between the bottom wall portion (Yb) and the cover bottom wall portion (Cb). Vent holes (hc, hy) communicating the ventilation clearance (21) with an outside of the yoke are provided through the bottom wall portion (Yb) and the cover bottom wall portion (Cb).
