Provided is a working machine including first and second members, an angle detection device and a connection pin connected to the first and second members to rotate integrally with the second member relative to the first member. The angle detection device has a marker, an angle sensor and a guard member, which has a main guard portion covering the angle sensor and including an inner opposite surface opposed to an end surface of the projecting end portion and a guard-member-side engagement portion. One of the angle sensor and the marker is disposed on the inner opposite surface, the other disposed on the end surface. The first member has a first-member-side engagement portion engaging with the guard-member-side engagement portion to restrain the main guard portion from relative rotation. The guard member can contact with the connection pin to restrain the guard member from relative displacement to the projecting end portion.