A billet for a thixocasting process and a thixocasting process using the billet allows casting using a thixocasting process to be realized at low production cost without permeation of an oxide film to the inside of the billet in injection molding. In a billet used for a thixocasting process continuously cast by intermittently drawing out, the interval of the oscillation marks is 10 mm or less and the maximum tilt angle of the oscillation marks relative to a cross section which is at a right angle to the drawing out direction is 45null or less.