A polyimide compound has a low coefficient of linear thermal expansion comparable to the coefficient of linear thermal expansion of a conductor to be covered by the polyimide. The polyimide compound is less susceptible to contraction caused by dehydration process. The compound is obtained by the reaction of a highly linear acid dianhydride with a highly linear diamine and has a high imidization rate. Having a low coefficient of linear thermal expansion comparable to the conductor to be covered by the polyimide, the polyimide compound of the present invention is less susceptible to contraction that occurs during polyimide formation. The polyimide compound is suitable for making curl-free flexible wiring boards.