The invention provides a heat dissipation device of an air blower and belongs to the technical field of fan devices. The problem that a motor of an existing air blower difficultly and effectively dissipates heat is solved. The air blower comprises an air barrel and a motor, wherein the motor is provided with a motor housing, the motor housing is fixedly connected with the air barrel, an air outlet pipe is connected to the air barrel, a branch pipe is fixedly connected to the air outlet pipe, one end of the branch pipe is communicated with the air outlet pipe, the other end of the branch pipe is communicated with the inner cavity of the motor housing, and a flow guide plate is rotatably connected in the air outlet pipe and is connected with an adjusting part. The heat dissipation device of the air blower can conduct timely and moderate heat dissipation and temperature reduction on the motor and is convenient to use.