An axial flow blower comprises a housing having a suction opening and an ejection opening formed thereon and having an air blow passage formed therein through which the suction opening and the ejection opening are in communication with each other, a motor case disposed in the air blow passage, a motor housed in the motor case, an air blow fan connected with a driven section of the motor and configured to rotate on a driving force of the motor to blow air from the suction opening toward the ejection opening and an air communication passage provided between an outside of the air blow passage and an inside of the motor case. An outflow hole is bored through the motor case and in communication with the air blow passage and an outer space outside the housing is in communication with an inner space inside the motor case through the air communication passage.
