Non-invasive evaluation technology of the skin is highly required for understandings of its properties as well as maintenance of healthy skin by cosmetic approach. Recently, various optical technologies have been proposed to measure inside of the skin. In this review, we introduce two topics. Confocal Raman spectroscopy enables us to detect not only water gradient beneath the skin surface, but also various constituents of the skin. Multi-photon microscopy provides visualization of dermal matrices including collagen fibers and elastin, and differences between subjects with less or much UV exposure history were successfully demonstrated, suggesting alteration in photo-aging. Such optical systems offer new insights thorough evaluation of inside of the skin with non-invasive fashion.