A working machine includes a base machine and a working attachment. The working attachment has a base-end boom, a lead-end boom, and an arm. The working machine is collapsible into a triple-folded state, with the base-end boom being located on the upper side and the arm being located on the lower side with respect to the lead-end boom, as a posture of the working machine for transport. The working machine further includes a lead-end boom cylinder for moving the lead-end boom, and an arm cylinder for moving the arm. The lead-end boom has a first lead-end boom cylinder attachment portion for mounting the lead-end boom cylinder, and a first arm cylinder attachment portion for mounting the arm cylinder. The first lead-end boom cylinder attachment portion is disposed at a position different from the first arm cylinder attachment portion in a widthwise direction of the working attachment, and lower than the first arm cylinder attachment portion in the transport posture.