To obtain the subject new compound excellent in surface wettability and transparency and having proper hardness and oxygen permeability.

This compound is expressed by formula I [Z1 and Z2 are each a group expressed by formula II (R3 is a 1-10C alkylene), etc.], e.g. the compound expressed by formula III. The compound expressed by formula I is obtained by, e.g. subjecting trimellitic acid anhydride chloride and the first monomer having a hydroxy group and a polymerizable unsaturated double bond to esterification in the presence of a tertiary amine in a solvent, such as benzene, at room temperature or below to synthesize trimellitic anhydride having a polymerizable unsaturated double bond expressed by formula V (Z3 is a group expressed by formula II, etc.), and subjecting this anhydride and the second monomer having a hydroxy group and polymerizable unsaturated double bond to esterification in the presence of a tertiary amine in a solvent, such as ethyl acetate at about 50°C.