Yokoyama was born in Nagasaki Prefecture on April 10, 1956. After graduating from Shimabara Technical High School, he joined Japan Soccer League Division 1 club Nippon Steel in 1975. However the club performance was not good, the club was relegated to Division 2 in 1982. He retired end of 1986/87 season. He played 105 games and scored 29 goals in Division 1.