A binding machine for gardening comprising: a binding machine main body; a clincher arm that is rotatably attached to the binding machine main body and that is configured to draw a tape out of the binding machine main body and to bind an object to be bound which is wound by the tape; and a cutting portion that is configured to cut the tape to be bound by the clincher arm, wherein the cutting portion includes: a blade that is configured to cut the tape; and a lock mechanism that is configured to fix the blade at a predetermined position of the binding machine main body, the lock mechanism has an operation portion (54, 54a, 54b) configured to lock and unlock the blade to and from the binding machine main body, characterized in that the operation portion (54, 54a, 54b) is formed by a release button, the release button including an enlarged diameter portion, the blade includes a saw-shaped teeth formed at a front end portion thereof and a recessed portion formed at a base end portion, wherein the lock mechanism further comprises an elastic member configured to urge the release button; and an elastic member support member, wherein the release button is urged by the elastic member and the enlarged diameter portion of the release button is positioned in the recessed portion of the blade such that the recessed portion is hooked to the enlarged diameter portion of the release button, so that the blade is locked. a binding machine main body; a clincher arm that is rotatably attached to the binding machine main body and that is configured to draw a tape out of the binding machine main body and to bind an object to be bound which is wound by the tape; and a cutting portion that is configured to cut the tape to be bound by the clincher arm, wherein the cutting portion includes: a blade that is configured to cut the tape; and a lock mechanism that is configured to fix the blade at a predetermined position of the binding machine main body, the lock mechanism has an operation portion (54, 54a, 54b) configured to lock and unlock the blade to and from the binding machine main body, characterized in that the operation portion (54, 54a, 54b) is formed by a release button, the release button including an enlarged diameter portion, the blade includes a saw-shaped teeth formed at a front end portion thereof and a recessed portion formed at a base end portion, wherein the lock mechanism further comprises an elastic member configured to urge the release button; and an elastic member support member, wherein the release button is urged by the elastic member and the enlarged diameter portion of the release button is positioned in the recessed portion of the blade such that the recessed portion is hooked to the enlarged diameter portion of the release button, so that the blade is locked. a blade that is configured to cut the tape; and a lock mechanism that is configured to fix the blade at a predetermined position of the binding machine main body, the lock mechanism has an operation portion (54, 54a, 54b) configured to lock and unlock the blade to and from the binding machine main body, characterized in that the operation portion (54, 54a, 54b) is formed by a release button, the release button including an enlarged diameter portion, the blade includes a saw-shaped teeth formed at a front end portion thereof and a recessed portion formed at a base end portion, wherein the lock mechanism further comprises an elastic member configured to urge the release button; and an elastic member support member, wherein the release button is urged by the elastic member and the enlarged diameter portion of the release button is positioned in the recessed portion of the blade such that the recessed portion is hooked to the enlarged diameter portion of the release button, so that the blade is locked.