A cabinet capable of guiding light, which is used for detecting a biological sample strained with a fluorescent dye, includes a main body, at least one light source, and at least one light guiding structure. The main body has a sample table to place the biological sample. The at least one light source is provided on the main body and near the sample table, wherein the at least one light source provides light required to excite the fluorescent dye incorporated in the biological sample. The at least one light guiding structure is provided between the sample table and the at least one light source to refract the light provided by the at least one light source onto the sample table and the biological sample. Whereby, the biological sample is exposed to more light, and therefore the intensity of the light released from the biological sample is enhanced.