To prevent contamination by silicone oil seeped out of a silicone sealing member.

The silicone oil seeping preventing agent is composed of four components, that is, a petroleum hydrocarbon, a photocatalytic titanium oxide, methylmethoxysiloxane, and either one of smectite, colloidal silica, zeolite and diatomite. Examples of the petroleum hydrocarbon are a mineral spirit, toluene, xylene, hexane, n-decane, etc. Smectite includes montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, stevensite, etc. It is further preferable to add to the above-described four components, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, etc., as a coupling agent.