Photoresponsive stilbenes with imidazolium cation directly attached to the para-position of the phenyl ring were prepared and their properties were examined. Although the cis isomer was liquid at room temperature and practically gave no fluorescence, the trans isomer was solid and gave fluorescence emission with quantum yield as high as ca. 0.2. Furthermore photoisomerization from pure cis isomer in the liquid state to trans isomer in the solid state was observed.