Transient absorption spectra of 1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-(2H)-indole] (6-nitro-BIPS) microcrystalline powder were measured by femtosecond diffuse reflectance spectroscopy and compared with those in the benzene solution and in a PMMA film. A very similar photochromic reaction occurs even in the crystal, although the structure of the generated photo-colored form in crystalline phase is not as planar as that of a stable form (trans-planar merocyanine) in solution. Photocoloration and the following thermal back reaction dynamics are considered in terms of free volume of the matrix and limited motion of the molecule.