PROBLEM TO BE SOLVED: To provide a miniaturizable timing adjusting device having good sealability and fewer components. SOLUTION: A shoe housing 3 comprises a peripheral wall 4 and a front plate 5, and is integrally formed by aluminum die casting. The shoe housing 3 is formed separately from a timing gear 1. The shoe housing 3 and the timing gear 1 constitute a housing member, so that the number of components is reduced and the sealability is improved. Outer diameter of the timing gear 1 can be decreased regardless of the outer diameter of the shoe housing 3. A seal member 16 is arranged in a sliding part between the peripheral wall 4 and a vane rotor 9. The seal member 16 is mainly made of PPS resin, and inorganic filler harder than the PPS resin is mixed to it. The PPS resin and the mixed inorganic filler are softer than the shoe housing 3, so that abrasion amount of the peripheral wall 4 is reduced.