The present invention provides a blade breakage and abrasion detecting device comprising: a detecting unit including a light-emitting unit which is provided close to a side of a blade to emit a round shape light toward the blade, and a light receiving unit which is provided opposed to the light-emitting unit as sandwiching the blade to receive the round shape light from the light-emitting unit with a round shape light receiving area; a moving device which moves the detecting unit toward a rotation center of the blade; and a control unit which detects a breakage of the blade based on a change of an amount of light received by the light receiving unit of the detecting unit, and calculates an abrasion amount of the blade by accumulating a moving amount obtained by controlling the moving device to moves the detecting unit toward the rotation center of the blade.