The invention provides a component of a substrate processing device and a film forming method avoiding generation of the particle of the damage caused by the eroded aluminum film. The cooling board (36) of the component of the substrate processing device (10) implementing the plasma process for the wafer (W) comprises the aluminum material (56) including the alloy with the silicon; and the erosion proofing aluminum film (57) formed on the surface of the aluminum material (56) dipped in the solution using the oxalic acid as main ingredient connected to the anode of the cooling board (36); the erosion proofing aluminum film (57) contains the silicic acid ethyl ester.