As ammonia manufacture today require huge energy and very pure hydrogen gas and moreover emit large quantities of CO2, researches for new ammonia synthesis methods are actively performed. Here, author reports the novel method through which N2molecules in air is reduced into ammonia with TiO2/Fe3O4composite having thin water layer on composite’s surface under ambient condition (less than 100 °C and atmospheric pressure). The composites were composed of both nm-sized TiO2particles and μm-sized Fe3O4ones. First, composites were held in refrigerator, mainly at that time, N2molecules in air adsorbed onto surface of composite. Next, the composite was irradiated with various lights including solar light, 365 nm LED light and tungsten light through thin water layer formed by condensation of water vapour in air. Reliable amount of ammonia was obtained under 5 min’s irradiation of solar light or of both 365 m LED light and 500 W tungsten light. This reaction was catalytic reaction promoted by photocatalytic one. In addition, holding in freezer instead of refrigerator provided larger amount of ammonia. Maximum ammonia yield was approximately 18.7 μmol/g 5 min under irradiation of 300 W tungsten light only.