And polyimide having (A) an acidic functional group, (B) a resin composition comprising a compound having a functional group which the acidic functional group and the reaction, (a) 90 ℃, 3% by weight hydroxide in 45 ℃ after the thermal history of 10 minutes the dissolution rate in aqueous solution, and to a thermal history prior to 1 0.95 or more, (b) 180 ℃, the dissolution rate of the 3% aqueous solution of sodium hydroxide at 45 ℃ after the thermal history of 60 minutes, 0.001 ㎛ / sec is more than 0.02 ㎛ / second or less, (c) 180 ℃, after heat history of 60 minutes, and bleed-out amount is 50 mg / m ² or less when kept for 2 weeks in 40 ℃, also, (d) a thermogravimetric analysis (TG ) by a, not more than a 2.0% decrease in the weight column 260 ℃ measured in the temperature rising condition of 10 ℃ / min from 40 ℃. The alkali workability, embedding, heat resistance, flex resistance, insulation reliability and the conductive layer may excellent adhesion of the resin layer of the press and during the preparation of a multilayer flexible wiring board is obtained by using the resin composition.