The invention provides a high pressure tank and provides a technique which suppresses idle rotation of a liner in the high pressure tank which is provided with the linear and a mouthpiece. The high pressure tank comprises a tank main body including a liner made of a resin and a mouthpiece made of a non-resin material and mounted to an open end of the liner; and a reinforcement layer provided to cover the entire tank main body and have pressure resistance. The liner includes a first contact surface arranged approximately perpendicular to a central axis of the liner to come into contact with the mouthpiece. The mouthpiece includes a second contact surface arranged to come into contact with the first contact surface of the liner. One of the first contact surface and the second contact surface includes projections, and the other includes recesses in which the projections being fitted. The second contact surface is formed in an approximately circular shape.