PURPOSE: To make a uniform crystal growth on a sample by scanning the sample so that any part of the sample may get a part of the laser beam which has a strong luminous intensity, 80% or more of the maximum intensity, during laser annealing.

CONSTITUTION: The laser light oscillated from a pulse light source 1 in which the ArF eximer laser is used is led to a beam scanner 3 through an optical system 2 and is cast on a sample 4 from the beam scanner 3. With the center of the beam being slided, the beam is cast on the sample so that any part of the sample may get the central part of the beam more than one time. Thus, the whole surface of the sample is annealed. A doughnut region 5 apart from the center of the pulse by the specified distance has the strongest luminous intensity (80% or more if the maximum value is 1). The sample is subjected to laser heat treatment by being scanned by the beam with the pulse being slided so that any part of the sample may get the doughnut region 5 at least one time.