In August, 1459, his father Yoshitoshi made Shogun Yoshimasa ASHIKAGA angry and was deprived of his position as shugoshiki (military governor) of 3 provinces, and secluded to the Ouchi clan, therefore Yoshihiro SHIBA succeeded the reigns of the Shiba family and shugoshiki of 3 provinces at the age of 3 under Echizen shugo the Kai clan's support.
長禄3年（1459年）8月、父義敏が将軍足利義政の怒りに触れ、3ヶ国の守護職を奪われ大内氏の許へ隠退すると、越前守護代甲斐氏らにより擁立され、僅か3歳で斯波氏家督と3ヶ国守護職を継ぐ。