A plug member of a gas valve, having an axial bore, a first bore and a second bore located in a radial direction thereof to respectively communicate with the axial bore, and a first guiding slot and a second guiding slot recessed into an outer peripheral surface thereof. The first bore is larger than the second bore, and communicates with one end of the first guiding slot, while another end thereof is near the second bore. The first guiding slot becomes narrower from the first end to the second end. The second guiding slot has one end communicating with the second bore, and another end located between said first end and said second end.