The invention discloses a wire saw cutting device and a coal seam gas permeability-increasing pressure-relieving method, and relates to the field of coal seam gas pressure relieving. The device comprises a wire saw machine and an adjusting piece. The method comprises the steps that S1, the effective drainage radius after slotting of the wire saw machine is determined; S2, the drilling density andposition are determined according to the effective drainage radius, and drilling is conducted; and S3, the whole coal seam is subjected to cutting slotting through the wire saw machine. According to the device and the method, a large free space is formed in a coal body through whole-face cutting of a coal seam, surrounding coal bodies move, deform and generate flowing deformation in the directionof the free space, the stress balance of the coal body is continuously and repeatedly broken, and finally, the coal body is in a new balance state; when the coal body is cut, a new crack is formed inthe coal body, the new crack and a primary crack and a free space pore system expand, intersect and communicate, and the gas permeability of the coal body is improved; and after slotting, a space is provided for expansion deformation of the surrounding coal bodies, the expansion deformation causes expansion and mutual penetration of pore and crack systems in the coal body, favorable conditions areprovided for efficient desorption and high-speed flowing of gas, the original property of the coal body is changed, and the outburst risk of a coal seam area is quickly eliminated.