A binding machine comprising: a body part; a cover guide part attached to the body part; a movable part (9AL, 9AR) provided to a side part of the body part and having a guided part (90AL, 90AR), a contact member (91AL, 91AR) and a detection part (93AL, 93AR), wherein the contact member (91AL, 91AR) is configured to be butted against a binding object, wherein the movable part (9AL, 9AR) is provided to be movable along a moving direction from a standby position, in which the contact member (91AL, 91AR) 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 can be inserted/pulled out, to an actuation position; and a sensor (312L, 312R) configured to detect the detection part (93AL, 93AR) of the movable part (9AL, 9AR), which detection part intersects with the moving direction (Al), so as to detect a movement of the movable part (9AL, 9AR) 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 (13L, 13R) 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 (11L, 11R) of the cover guide part with a long-hole-shaped opening extending in the moving direction of the movable part (9AL, 9AR), the movable part (9AL, 9AR) includes a guide convex portion (94AL1, 94AL2, 94AR1, 94AR2) provided on one surface of the guided part (90AL, 90AR) facing toward the sidewall part (11L, 11R) of the cover guide part, protruding in a direction orthogonal to the moving direction of the movable part (9AL, 9AR), 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 (9AL, 9AR) to the actuation position until the binding object reaches a position at which the binding object is butted against the contact part (13L, 13R). a body part; a cover guide part attached to the body part; a movable part (9AL, 9AR) provided to a side part of the body part and having a guided part (90AL, 90AR), a contact member (91AL, 91AR) and a detection part (93AL, 93AR), wherein the contact member (91AL, 91AR) is configured to be butted against a binding object, wherein the movable part (9AL, 9AR) is provided to be movable along a moving direction from a standby position, in which the contact member (91AL, 91AR) 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 can be inserted/pulled out, to an actuation position; and a sensor (312L, 312R) configured to detect the detection part (93AL, 93AR) of the movable part (9AL, 9AR), which detection part intersects with the moving direction (Al), so as to detect a movement of the movable part (9AL, 9AR) 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 (13L, 13R) against which the binding object is to be butted, whereby a guide part configured to movably guide the movable part, and a contact part (13L, 13R) 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 (11L, 11R) of the cover guide part with a long-hole-shaped opening extending in the moving direction of the movable part (9AL, 9AR), the movable part (9AL, 9AR) includes a guide convex portion (94AL1, 94AL2, 94AR1, 94AR2) provided on one surface of the guided part (90AL, 90AR) facing toward the sidewall part (11L, 11R) of the cover guide part, protruding in a direction orthogonal to the moving direction of the movable part (9AL, 9AR), 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 (9AL, 9AR) to the actuation position until the binding object reaches a position at which the binding object is butted against the contact part (13L, 13R).