A power transmission device that can reliably prevent engine stall from occurring. This provides a high degree of freedom of patterning of the antenna circuit. By means of this, the installed floor area of the plant is dramatically reduced, and it is also possible to reduce construction costs. A seat moving mechanism is provided between the seats and the vehicle body, for holding the plurality of seats such that the plurality of seats can move in the direction of the width of the vehicle body, and moving the plurality of seats from the cab rearward onto the bed and holding the plurality of seats. The invention also includes a method for purifying the non-ionic contrast agents.