To provide a hot forming method for titanium alloy cylindrical parts in which the number of welding parts is reduced, and the number of hot formings per product is reduced.

Blanking of a plate 1 is performed in (a), a cylindrical parts 2 is formed by performing the welding 3 after the plate is formed in a cylindrical shape in (b), a sectional die holder 13 and the cylindrical parts 2 are pressed against a die 12 within a heating furnace 15 by a punch 10 in (c), and hot- formed at the temperature of 680-720°C. After the hot forming, the completed cylindrical parts 4 is taken out as shown in (d). The sectional die holder 13 connects upper portions of eight split pieces by a ring, and fits lower portions thereof to a base in a radially mobile manner. When a wedge-like projection part 11 is inserted, each split piece is expanded outwardly to expand the cylindrical parts, and the cylindrical parts is hot-formed. Welding 3 may be performed only once.