A synthetic anthocyanin pigment, 2-hydroxy-4’-methoxychalcone (HMC), has the same molecular skeleton as plant pigments and promises to be practically applicable as a safe and environmentally friendly photochromic pigment. With the objective of using HMC in dry conditions, we prepared a composite of silica and HMC and investigated its photochromic properties. In order to maximize the adsorption of HMC onto silica, we prepared a HMC solution with UV-A irradiation at pH 3.7 in which HMC was mainly in the flavylium cation form. Unlike the HMC solution, the HMC/silica composite did not exhibit optical decoloring under UV-C irradiation : only coloration was observed under UV-A irradiation. On the other hand, decoloration occurred in the dark within five days, and occurred more readily at a higher temperature and higher humidity than normal.