Provided are a side member from which a clad member for heat exchanger exhibiting excellent productivity and corrosion resistance while preventing poor adhesion can be produced in production of a clad member for heat exchanger by controlling the surface state and flatness, a method for producing the side member, and a method for producing a clad member for a heat exchanger by using the side member. A side member (A) consists of a core material and one or more layers of side member (A) applied onto one side or both sides thereof and being used in a clad member for a heat exchanger, wherein a plurality of periodic forms (B) of fine groove which become arcuate toward one direction of the side member (A) is formed on the surface of the side member (A). The periodic form (B) of fine groove extends up to the outer circumferential edge of the side member (A) with a radius of curvature of 800-1500 mm and has a period (D) of 1-8 mm in the above-mentioned direction of the side member (A) and surface roughness of the side member (A) in the above-mentioned direction of 1-15 μm 10-point average roughness (Rz).