There is provided a Co-based alloy material, having a chemical composition including: Al of 0.1 to 10 mass %; W of 3 to 45 mass %, the total content of Al and W being 50 mass % or less; O of 0.007 to 0.05 mass %; and the balance being Co and impurities, wherein in γ phase crystal grains as a matrix phase of the Co-based alloy material, segregation cells within an average size of 0.15 to 1.5 μm are formed, wherein in the segregation cells, γ′ phase grains within a size of 0.01 to 0.5 μm including Co, Al and W are dispersively precipitated, and wherein on boundary regions of the segregation cells and grain boundaries of the γ phase crystal grains, μ phase grains within a size of 0.005 to 2 μm including Co and W are dispersively precipitated.