Provided are a decompression shut-off valve device having high responsiveness and a method for controlling the same. The decompression shut-off valve device 10 includes an on-off valve 30, a detection pin 50, and an interlocking member 60 which operates the on-off valve 30 by displacement of the pressure-receiving section 52, a valve chamber 31, an accommodating chamber 17, and a cylinder 40 which accommodates an enlarged diameter section 37 provided in a rod section 33 of the on-off valve 30. The rod section 33 is slidably held through a second partition wall 18, and a rod end portion 36 of the rod section 33 is connected to the detection pin 50 via the interlocking member 60. The cylinder 40 is partitioned into a small diameter low-pressure chamber 80, and a large diameter high-pressure chamber 70 in which the working fluid having a higher pressure than the low-pressure chamber 80 is accommodated.