DUAL-FUEL GAS ENGINE AND FUEL GAS INJECTION METHOD

A fuel gas injection valve according to the present invention includes: a holder (22) including a first injection hole (61) through which fuel gas is injected to produce premixed fuel, and a second injection hole (62) through which fuel gas is injected to produce diffusion fuel; a first needle valve (23) that slidably reciprocates in the holder (22) along an axial direction to open and close the first injection hole (61) and the second injection hole (62); and a second needle valve (25) having a sealing face (94) on the top thereof and a through-hole (91) provided along the axial direction at the central portion in a radial direction of the second needle valve (25), the sealing face being brought into contact with a needle valve seat (93) provided in the holder (22), the first needle valve (23) being slidably inserted into the through-hole, and the second needle valve (25) reciprocating in the holder (22) along the axial direction to prevent fuel gas from circulating to the first injection hole (61) and the second injection hole (62) when the sealing face (94) is in contact with the needle valve seat (93), and to allow the fuel gas to circulate to the first injection hole (61) or the second injection hole (62) when the sealing face (94) is separated from the needle valve seat (93).