A reflective Ag alloy film includes a Ag--Bi alloy thin film, and a Bi layer and/or a Bi oxide layer formed on the surface and/or between the Ag--Bi alloy thin film and another layer formed on the Ag--Bi alloy thin film. The thickness of the Bi layer and/or the Bi oxide layer is 2.0 nm or below. The Ag--Bi alloy thin film of the reflective Ag alloy film has a Bi content in the range of 0.01 to 3.0 at %. A reflector is formed by depositing the Ag--Bi alloy thin film on a base member.