A laser beam 6 irradiated from a side face of a microchip 1 in which plural channels 2 fill ed with a member of a refractive index n2 in an inner portion of a member of a refractive index n1 (n2 lower base, and is deviated swiftly from a channel array. Hence, the laser beam 6 is made to be deviated gradually from the channel array by irradiating the laser beam 6 from the side face of the microchip 1 by being inclined relative to the same plane in a direction of being directed from the lower base to the upper base. As a result, a larger number of the channels 2 can efficiently be subjected to laser beam irradiation.