A novel polyimide compound which has a low linear expansion coefficient and permits film formation by a spin coating method or the like, a preparation method for the polyimide compound, and an optical film and an optical waveguide produced by employing the compound. The polyimide compound has a structural unit represented by the following general formula (1): wherein X is a covalent single bond, —CH2—, —C(CF3)2— or —CR(R′)— (wherein R and R′, which may be the same or different, are each a C1 to C6 alkyl group or an aryl group); A and B, which may be the same or different, are substituents each selected from a hydroxyl group, a halogen group and a C1 to C4 alkyl group; a and b, which are the numbers of the substituents A and B, respectively, are each an integer of 0 to 2; and o, p and q are each an integer of 1 to 5.