A power tool comprising: a motor; a fan configured to be rotated by the motor to generate a cooling air; a housing (44, 45, 46; 144, 145; 244; 344) accommodating therein the motor and the fan and defining an air passage for the cooling air; an output shaft rotatable by the motor, an end bit being attachable to and detachable from the output shaft; and a transmission mechanism configured to transmit rotation of the motor to the output shaft, wherein the transmission mechanism comprises: an intermediate shaft provided in the housing (44, 45, 46; 144, 145; 244; 344); a first pulley configured to rotate in synchronization with the motor; a second pulley (55; 155); a third pulley, each of the second pulley (55; 155) and the third pulley being rotatable about an axis of the intermediate shaft; a first belt looped over the first pulley and the second pulley (55; 155) so as to transmit a rotational force of the motor to the intermediate shaft; a pulley (51; 251) configured to rotate in synchronization with the output shaft; and a second belt looped over the third pulley and the pulley (51; 251) so as to transmit a rotational force of the intermediate shaft to the output shaft, and wherein the housing (44, 45, 46; 144, 145; 244; 344) comprises a case (44; 144; 244; 344) accommodating therein the pulley (51; 251) and the third pulley, characterized in that: an outlet port (71, 72, 73) through which the cooling air is discharged outside the case (44; 144; 244; 344) is formed at an outer peripheral surface portion of the case (44; 144; 244; 344); and the first pulley, the second pulley (55; 155), and the third pulley, the motor, the first belt and the second belt are positioned inside the air passage. a motor; a fan configured to be rotated by the motor to generate a cooling air; a housing (44, 45, 46; 144, 145; 244; 344) accommodating therein the motor and the fan and defining an air passage for the cooling air; an output shaft rotatable by the motor, an end bit being attachable to and detachable from the output shaft; and a transmission mechanism configured to transmit rotation of the motor to the output shaft, wherein the transmission mechanism comprises: an intermediate shaft provided in the housing (44, 45, 46; 144, 145; 244; 344); a first pulley configured to rotate in synchronization with the motor; a second pulley (55; 155); a third pulley, each of the second pulley (55; 155) and the third pulley being rotatable about an axis of the intermediate shaft; a first belt looped over the first pulley and the second pulley (55; 155) so as to transmit a rotational force of the motor to the intermediate shaft; a pulley (51; 251) configured to rotate in synchronization with the output shaft; and a second belt looped over the third pulley and the pulley (51; 251) so as to transmit a rotational force of the intermediate shaft to the output shaft, and wherein the housing (44, 45, 46; 144, 145; 244; 344) comprises a case (44; 144; 244; 344) accommodating therein the pulley (51; 251) and the third pulley, characterized in that: an outlet port (71, 72, 73) through which the cooling air is discharged outside the case (44; 144; 244; 344) is formed at an outer peripheral surface portion of the case (44; 144; 244; 344); and the first pulley, the second pulley (55; 155), and the third pulley, the motor, the first belt and the second belt are positioned inside the air passage. an intermediate shaft provided in the housing (44, 45, 46; 144, 145; 244; 344); a first pulley configured to rotate in synchronization with the motor; a second pulley (55; 155); a third pulley, each of the second pulley (55; 155) and the third pulley being rotatable about an axis of the intermediate shaft; a first belt looped over the first pulley and the second pulley (55; 155) so as to transmit a rotational force of the motor to the intermediate shaft; a pulley (51; 251) configured to rotate in synchronization with the output shaft; and a second belt looped over the third pulley and the pulley (51; 251) so as to transmit a rotational force of the intermediate shaft to the output shaft, and wherein the housing (44, 45, 46; 144, 145; 244; 344) comprises a case (44; 144; 244; 344) accommodating therein the pulley (51; 251) and the third pulley, characterized in that: an outlet port (71, 72, 73) through which the cooling air is discharged outside the case (44; 144; 244; 344) is formed at an outer peripheral surface portion of the case (44; 144; 244; 344); and the first pulley, the second pulley (55; 155), and the third pulley, the motor, the first belt and the second belt are positioned inside the air passage. an outlet port (71, 72, 73) through which the cooling air is discharged outside the case (44; 144; 244; 344) is formed at an outer peripheral surface portion of the case (44; 144; 244; 344); and the first pulley, the second pulley (55; 155), and the third pulley, the motor, the first belt and the second belt are positioned inside the air passage.