A binding machine comprising: a body part ; a cover guide part attached to the body part ; a movable part provided to a side part of the body part and having a guided part , a contact member and a detection part , wherein the contact member is configured to be butted against a binding object, wherein the movable part is provided to be movable along a moving direction (A1) from a standby position, in which the contact member protrudes into an insertion/pulling-out opening formed between a first guide and a second guide of the binding machine, in and from which reinforcing bars (S) can be inserted/pulled out, to an actuation position; and a sensor configured to detect the detection part of the movable part , which detection part intersects with the moving direction (Al), so as to detect a movement of the movable part to the actuation position and thus to cause the binding machine to execute an operation of binding, wherein the cover guide part includes: a guide part configured to movably guide the movable part, and a contact part against which the binding object is to be butted, whereby the guide part includes a guide concave portion (14L1, 14L2, 14R1, 14R2) provided in a sidewall part of the cover guide part with a long-hole-shaped opening extending in the moving direction of the movable part , the movable part includes a guide convex portion (94AL1, 94AL2, 94AR1, 94AR2) provided on one surface of the guided part facing toward the sidewall part of the cover guide part , protruding in a direction orthogonal to the moving direction (A1) of the movable part , and inserted into the opening of the guide concave portion (14L1, 14L2, 14R1, 14R2), and the guide concave portion (14L1, 14L2, 14R1, 14R2) defines a moving amount of the movable part to the actuation position until the binding object reaches a position at which the binding object is butted against the contact part . a body part ; a cover guide part attached to the body part ; a movable part provided to a side part of the body part and having a guided part , a contact member and a detection part , wherein the contact member is configured to be butted against a binding object, wherein the movable part is provided to be movable along a moving direction (A1) from a standby position, in which the contact member protrudes into an insertion/pulling-out opening formed between a first guide and a second guide of the binding machine, in and from which reinforcing bars (S) can be inserted/pulled out, to an actuation position; and a sensor configured to detect the detection part of the movable part , which detection part intersects with the moving direction (Al), so as to detect a movement of the movable part to the actuation position and thus to cause the binding machine to execute an operation of binding, wherein the cover guide part includes: a guide part configured to movably guide the movable part, and a contact part against which the binding object is to be butted, whereby a guide part configured to movably guide the movable part, and a contact part against which the binding object is to be butted, whereby the guide part includes a guide concave portion (14L1, 14L2, 14R1, 14R2) provided in a sidewall part of the cover guide part with a long-hole-shaped opening extending in the moving direction of the movable part , the movable part includes a guide convex portion (94AL1, 94AL2, 94AR1, 94AR2) provided on one surface of the guided part facing toward the sidewall part of the cover guide part , protruding in a direction orthogonal to the moving direction (A1) of the movable part , and inserted into the opening of the guide concave portion (14L1, 14L2, 14R1, 14R2), and the guide concave portion (14L1, 14L2, 14R1, 14R2) defines a moving amount of the movable part to the actuation position until the binding object reaches a position at which the binding object is butted against the contact part . <EOS>