A flat cutting tool includes a blade member fixed to a mounting concavity of a base member using a brazing filler metal or an adhesive agent to form a cutting edge on a surface layer side of the blade member. The blade member includes a surface layer which is a high-speed tool steel with a high degree of hardness, a middle layer which is an alloy steel having a lower quench-hardenability than the high-speed tool steel, and a lower layer which is a mild steel having little quench-hardenability, which can be formed by forge welding. The blade member can be quenched and tempered, and the surface layer hardened to a hardness suitable for the cutting tool and fixed to the mounting concavity of the base member.