PURPOSE: To easily connect a tie bar with a fixed die plate by engaging a collar with an annular groove arranged at one side of the tie bar, pushing one end face of the tie bar with hydraulic cylinder to the axial direction and loading a compressive preload.

CONSTITUTION: One or plural annular grooves 14 are arranged at one side of a fixed die plate 12 side in the tie bar 11. The collar 15 divided into plural pieces in the radius direction is fitted into this annular groove 14 by sliding it between the end face E of the fixed die plate 12 and a guide block 17, from the outer diameter direction by an actuator 16. Successively, oil pressure is applied to the hydraulic cylinder 19 fitted to the guide block 17 from a solenoid valve 23 through hydraulic ports 7, 8 to press the end face 22 of tie bar 11 with tip part 21 of the piston 20. The collar 15 is pushed to the fixed die plate 12 with this compressive preload through the shoulder face 24 in the above annular groove 14. By this method, the tie bar 11 is easily and surely fixed to the fixed die plate 12 without damaging the parts.