A rotary electric device for a power working machine, which is operatively connected to an engine as a power source for the power working machine, and capable of being braked by a brake mechanism, the rotary electric device comprising: a stator fixed to an engine main body (Em); a yoke including a bottom wall portion (Yb) and a cylindrical portion (Yc) which surrounds the stator, the yoke being formed in a bottomed cylindrical shape by connecting the bottom wall portion (Yb) to one end of the cylindrical portion (Yc), and the yoke being connected to a crankshaft of the engine; a magnet fixedly attached to an inner peripheral surface of the cylindrical portion (Yc) of the yoke, and facing the stator, characterized in that said rotary electric device further comprises: a cover having a bottomed cylindrical shape, and covering the yoke, wherein the cover includes a cover cylindrical portion (Cc) concentrically surrounding an outer peripheral surface of the cylindrical portion (Yc) of the yoke with an annular clearance interposed therebetween, and having an outer peripheral surface with which a brake shoe (Bs) of the brake mechanism 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 the bottom wall portion (Yb) of the yoke, a ventilation clearance communicating with the annular clearance is formed between the bottom wall portion (Yb) of the yoke and the cover bottom wall portion (Cb), and vent holes (hy, hc) communicating the ventilation clearance with an outside of the yoke are provided through the bottom wall portion (Yb) of the yoke and the cover bottom wall portion (Cb). a stator fixed to an engine main body (Em); a yoke including a bottom wall portion (Yb) and a cylindrical portion (Yc) which surrounds the stator, the yoke being formed in a bottomed cylindrical shape by connecting the bottom wall portion (Yb) to one end of the cylindrical portion (Yc), and the yoke being connected to a crankshaft of the engine; a magnet fixedly attached to an inner peripheral surface of the cylindrical portion (Yc) of the yoke, and facing the stator, characterized in that said rotary electric device further comprises: a cover having a bottomed cylindrical shape, and covering the yoke, wherein the cover includes a cover cylindrical portion (Cc) concentrically surrounding an outer peripheral surface of the cylindrical portion (Yc) of the yoke with an annular clearance interposed therebetween, and having an outer peripheral surface with which a brake shoe (Bs) of the brake mechanism 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 the bottom wall portion (Yb) of the yoke, a ventilation clearance communicating with the annular clearance is formed between the bottom wall portion (Yb) of the yoke and the cover bottom wall portion (Cb), and vent holes (hy, hc) communicating the ventilation clearance with an outside of the yoke are provided through the bottom wall portion (Yb) of the yoke and the cover bottom wall portion (Cb). a cover having a bottomed cylindrical shape, and covering the yoke, wherein the cover includes a cover cylindrical portion (Cc) concentrically surrounding an outer peripheral surface of the cylindrical portion (Yc) of the yoke with an annular clearance interposed therebetween, and having an outer peripheral surface with which a brake shoe (Bs) of the brake mechanism 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 the bottom wall portion (Yb) of the yoke, a ventilation clearance communicating with the annular clearance is formed between the bottom wall portion (Yb) of the yoke and the cover bottom wall portion (Cb), and vent holes (hy, hc) communicating the ventilation clearance with an outside of the yoke are provided through the bottom wall portion (Yb) of the yoke and the cover bottom wall portion (Cb).