Method of manufacturing hollow body

A method of manufacturing a pipe-shaped hollow body having a bent portion, which comprises injecting a molten resin into a mold cavity of a mold, the mold cavity having on its one end a pressure port provided with a floating core and on its other end an outlet, pressure-injecting a pressurized fluid through the pressure port after the injection of the molten resin, and moving the floating core to the outlet side, and, at the same time, extruding the molten resin from the outlet, the method comprising:

• the floating core is constituted of a columnar portion and a top portion, which is continuously connected to one surface of the columnar portion and has a shape that a cross-sectional area perpendicular to a central axis of the columnar portion gradually decreases from one surface side of the columnar portion, and when a diameter of the columnar portion is represented by A, the height of the columnar portion is 0.1 A to 1 A, and the height of the top portion is 0.3 A to 1.6 A, wherein
• the floating core is fitted in the pressure port on the other surface side of the columnar portion, and
• a peripheral edge of the other surface of the columnar portion of the floating core is subjected to a corner rounding processing with a curvature radius of A/1000 to A/3.