1. A process for forming an antireflection film as adhered on a glass surface, which comprises preparing a reaction mixture comprising a silicon compound (A) of the following formula (1): 7 1-5 alkyl group, a silicon compound (B) of the following formula (2): 8 1 is a C 1-18 organic group, and R 2 is a C 1-5 alkyl group, an alcohol (C) of the following formula (3): 9 3 is a hydrogen atom or an unsubstituted or substituted C 1-12 alkyl group, and oxalic acid (D), in a ratio of from 0.05 to 4.5 mol of the silicon compound (B) per mol of the silicon compound (A), in a ratio of from 0.5 to 100 mol of the alcohol (C) per mol of the total alkoxy groups contained in the silicon compounds (A) and (B), and in a ratio of from 0.2 to 2 mol of the oxalic acid per mol of the total alkoxy groups contained in the silicon compounds (A) and (B); heating the reaction mixture at a temperature of from 50 to 180° C. until the total amount of the silicon compounds (A) and (B) remaining in the reaction mixture becomes at most 5 mol %, while maintaining a SiO 2 concentration of from 0.5 to 10 wt % as calculated from silicon atoms in the reaction mixture and maintaining absence of water, to form a polysiloxane solution; coating the polysiloxane solution on a glass surface to form a coating film; and heat-curing the coating film at a temperature of from 480 to 520° C.