An ultraviolet-laser excitation microscopic photothermal lens imaging system for observing chemical compounds in biological cells has been designed and constructed, in which a reflection objective lens is used for focusing an excitation laser beam at 261 nm and a probe laser beam at 784 nm. Photothermal amplitude and phase images of yeast fungus cells are successfully obtained; together with a transmitted light image at 784 nm. The amplitude image represents photo-absorption at 261 nm by the cells. The phase image seems to represent local thermal properties around the cells.