A working machine coupler device comprising: a top linkage configured to be pivotally supported on a traveling vehicle, the top linkage being configured to stretch and shorten; a lower linkage configured to be pivotally supported on the traveling vehicle; a detachable frame connecting the top linkage and the lower linkage, the detachable frame including: a second upper coupler configured to be coupled to a first upper coupler provided to a working machine; and a second lower coupler configured to be coupled to a first lower coupler provided to the working machine; and a top linkage controller mechanism to control stretching and shortening of the top linkage, wherein the second upper coupler and the second lower coupler are configured such that the second upper coupler of the detachable frame inclining backward is coupled to the first upper coupler when the lower linkage is pivoted upward, and the first lower coupler is configured to move toward and be coupled to the second lower coupler when a front portion of the working machine is moved upward, and the top linkage controller mechanism is configured to regulate the stretching and shortening of the top linkage to hold the detachable frame inclining backward, and allow the top linkage to be shortened until the working machine takes a working posture after the lower linkage is pivoted downward from a state where the front portion of the working machine is lifted, characterised in that the top linkage control mechanism includes an engagement groove and an engagement member to be engaged with the engagement groove, and the engagement groove includes a lock portion to be engaged with the engagement member to lock the stretching and shortening of the top linkage when the working machine takes the working posture. a top linkage configured to be pivotally supported on a traveling vehicle, the top linkage being configured to stretch and shorten; a lower linkage configured to be pivotally supported on the traveling vehicle; a detachable frame connecting the top linkage and the lower linkage, the detachable frame including: a second upper coupler configured to be coupled to a first upper coupler provided to a working machine; and a second lower coupler configured to be coupled to a first lower coupler provided to the working machine; and a second upper coupler configured to be coupled to a first upper coupler provided to a working machine; and a second lower coupler configured to be coupled to a first lower coupler provided to the working machine; and a top linkage controller mechanism to control stretching and shortening of the top linkage, wherein the second upper coupler and the second lower coupler are configured such that the second upper coupler of the detachable frame inclining backward is coupled to the first upper coupler when the lower linkage is pivoted upward, and the first lower coupler is configured to move toward and be coupled to the second lower coupler when a front portion of the working machine is moved upward, and the top linkage controller mechanism is configured to regulate the stretching and shortening of the top linkage to hold the detachable frame inclining backward, and allow the top linkage to be shortened until the working machine takes a working posture after the lower linkage is pivoted downward from a state where the front portion of the working machine is lifted, characterised in that the top linkage control mechanism includes an engagement groove and an engagement member to be engaged with the engagement groove, and the engagement groove includes a lock portion to be engaged with the engagement member to lock the stretching and shortening of the top linkage when the working machine takes the working posture.