The present invention relates to a flexible optical waveguide prepared by using a resin film for forming an optical waveguide for at least one of a lower cladding layer, a core layer and an upper cladding layer, wherein a ten point average roughness (Rz) on a surface of either one of the lower cladding layer and the upper cladding layer is 0.5 μm or more and 10 μm or less, a production process for the same and an optical module prepared by using the flexible optical waveguide. Provided are a flexible optical waveguide which is excellent in an adhesive property in compounding with an electric printed wiring board and turning a flexible optical waveguide into a multilayer, a production process for the same and an optical module prepared by using the flexible optical waveguide.