To provide a valve device comprising a valve sheet and a valve, capable of maintaining excellent anti-abrasion performance and low counterpart aggressivity even under a severe condition in which the valve device is used while intermetallic contact between a valve sheet and a valve is likely to occur as in an engine for a gas fuel.

In a valve device for an internal combustion engine comprising a valve sheet with a base body and a valve, the base body of the valve sheet contains a base material of iron group sintered alloy, and a dispersed Si-Cr-Mo- Co based intermetallic compound. The intermetallic compound, with hardness Hv of 600 to 1,000 and an average particle diameter of 20 to 70 μm, occupies 10 to 50 weight % with respect to the total weight of the base body. In a valve face of a base body of the valve, any layer among a nitride diffusion layer having hardness Hv of 500 or more and thickness of 20 μm or more, a stellite- based cobalt group alloy padding layer having hardness Hv of 400 or more and thickness of 0.5 mm or more, and an Si-Cr-Mo-Co based intermetallic compound padding layer having hardness Hv of 400 or more and thickness of 0.5 mm or more, is formed.