A luminous keyboard and an optical module thereof are provided. The optical module includes a light guide sheet, a reflective film on one side of the light guide sheet, and an optical film on another side of the light guide sheet opposite to the reflective film. The optical film has a mask pattern. The mask pattern defines a light-transparent region, a light-shielding region, and a light modulation region extending from the light-shielding region to the light-transparent region. The light-transparent region allows light to pass therethrough. The light-shielding region blocks light. The light modulation region partially allows light to pass therethrough and partially blocks light, so that an average light-transmitting rate per unit area of the light modulation region is smaller than that of the light-transparent region and larger than that of the light-shielding region.