To provide a laser irradiation apparatus which performs alignment of an irradiated object and emits a laser beam precisely, a laser irradiation method, and a manufacturing method of a TFT with high reliability with the use of a method for precisely targeting a desired irradiation position of the laser beam. A substrate with marker is mounted on a stage formed using a material which transmits infrared light; a marker, which is provided in the substrate with marker mounted on the stage, is detected using a camera capable of sensing infrared light, and a position of the stage is controlled; a laser beam is emitted from a laser oscillator; the laser beam emitted from the laser oscillator is processed into a linear shape by an optical system, and the substrate with marker mounted on the stage is irradiated with the laser beam.