A resin composition for an optical waveguide is provided, which comprises: an epoxy compound represented by the following general formula (1): wherein m is 1 or a positive integer, n is 1 or a positive integer, R and R′ which may be the same or different are each represented by the following formula (2) or (3), wherein c is a positive integer of 1 to 3 and each one of c may be the same or different, and X is represented by the following formula (4): wherein a is an integer of 0 to 2, and b is a positive integer of 1 to 3, and satisfy a condition of a+b=3; and a photoacid generator. The resin composition has a lower viscosity, and is excellent in flexibility and moisture absorption resistance. An optical waveguide produced by employing the resin composition is also provided.