A plug member of a gas valve includes a main body. The main body has an axial bore in an axial direction, a first inlet and a second inlet in radial directions, and a guiding slot on a surface. The first inlet and the second inlet are connected to the axial bore. A diameter of the first inlet is greater than a diameter of the second inlet. The guiding slot has a first end communicated with the first inlet and a second end communicated with the second inlet, and a width of the guiding slot gradually reduces from the first end to the second end. Therefore, the gas valve may provide a gas flow with a linear change by controlling the plug member.