Seizure resistance and wear resistance of Cu—Bi—In copper-alloy sliding material are enhanced by forming a soft phase of as pure as possible Bi. Mixed powder of Cu—In cuprous alloy powder and Cu—Bi containing Cu-based alloy powder is used. A sintering condition is set such that Bi moves outside particles of said Cu—Bi containing Cu-based powder and forms a Bi grain-boundary phase free of In, and In diffuses from said Cu—In containing Cu-based powder to said Cu—Bi containing Cu-based powder.