PURPOSE: To provide a filter for decomposing ozone having a lower pressure loss, a high decomposition capacity, and a long life.

CONSTITUTION: A cured product of a composition comprising 100 pts.wt. of a resol-type phenolic resin (a), 1-100 pts.wt. of a lipophilic compound (b) which is liquid at room temperature and has a boiling point of 100°C or higher, and 1-100 pts.wt. of a hydrophilic liquid compound (c) having a boiling point of 100°C or higher is carbonized and activated to obtain a porous structure of activated carbon. The structures are allocated in the air passage of a filter for decomposing ozone.