An interference filter includes first and second reflecting films opposed to each other across a gap, the first and second reflecting films include an Ag—Sm—Cu alloy film or an Ag—Bi—Nd alloy film, the Ag—Sm—Cu alloy film includes 0.1 atomic %≦Sm≦0.5 atomic %, and 0.1 atomic %≦Cu and ≦0.5 atomic %, and Sm+Cu≦1.0 atomic %, the Ag—Bi—Nd alloy film includes 0.1 atomic %≦Bi≦3.0 atomic %, and 0.1 atomic %≦Nd≦5.0 atomic %, and the thickness of the Ag—Sm—Cu alloy film or the Ag—Bi—Nd alloy film is ≧10 nm and ≦40 nm.