An illuminated keyboard includes a supporting plate, a bottom circuit membrane disposed on the support plate, an intermediate partition plate disposed above the bottom circuit membrane, and a top circuit membrane disposed above said intermediate partition plate. A light emitter unit is disposed on the bottom circuit membrane. A light diffusion layer is disposed above the top circuit membrane and has a light transmission region for transmitting light rays generated from the light emitter unit. An elastic member is made of an elastic material and disposed on and above the diffusion layer. A bridging unit is disposed above the diffusion layer and aligned with the elastic member. A keycap is disposed above and connected to the bridging unit. The elastic member elastically abuts against the keycap. The keycap is light permeable.