PURPOSE: To allow the simultaneous testing of the composite change of materials to be tested with various kinds of light by providing an oscillating body forming the standing waves of sounds within the pipe at one end of the test pipe through which various kinds of rays for irradiation can pass and a mechanism for adjusting the length of the pipeline, a pressure sensor, etc., at the other end.

CONSTITUTION: The standing waves of sounds from the oscillating body 4 exist in the test pipe 2 and the dense parts of the sound waves are high in gaseous pressure and the materials 28 to be tested float concentrically in these parts. The pressure sensor 12 is moved froward and backward with respect to the inside of the test pipe by the mechanism for adjusting the length of the pipeline under the control with a control means 22, by which the pressure sensor is moved and the floating positions of the materials to be tested are specified by the computation from the max. value of the output of the pressure sensor. An irradiation mechanism 24 is moved toward the position and the rays for irradiation are cost from the outside of the pipe. The change of the materials to be tested at every irradiation of the plural kinds is simultaneously tested, by which the test period is shortened and initial cost is reduced.