The photochromic behavior of spiroxazine by UV irradiation can be affected by some solvents surrounding the photochromic dye. To investigate this solvent effect, we formed a self-assembled monolayer of a synthesized spiroxazine derivative on a gold surface. The solvent effect on photochromic behavior was studied by using surface plasmon resonance (SPR). The subtle photochromic behavior of the monolayer in different solvents under UV irradiation can be measured efficiently through comparison of their SPR angle shifts.