To suppress a projecting amount of a plug portion of a composite pressure vessel, prevent transmission of local impact force from the plug portion even if the composite pressure vessel is dropped with a plug fitted, and prevent damage of a liner caused by the dropping.

The composite pressure vessel 1 is provided with the metallic liner 2 having boss parts 4, 5 formed in both end parts and a fiber-reinforced plastic layer 3 formed on the outer layer of the liner 2, and one boss part 5 is sealed by the plug 8. The outer diameter of a head of the plug 8 is set to be equal to or approximately equal to the outer diameter of the boss part 5, and the thickness of the fiber-reinforced plastic layer 3 formed around the boss part 5 is set to be equal to or higher by predetermined amount than the height of the head of the plug 8.