A scroll hydraulic machine comprising a housing having a key groove, a fixed scroll disposed in said housing, a swirling scroll having a key groove disposed in said housing, engaging with said fixed scroll, and moving in a swirling motion, and an Oldham ring provided with a swirling key engaging, in a freely sliding manner, with said key groove formed on said swirling scroll, and a fixed key engaging, in a freely sliding manner, with the key groove formed on said housing, and Sn plated on at least one side surface of the swirling key and the fixed key.