Irradiating a plurality of laser beams onto different microparticles or different groups of microparticles, and trapping and/or manipulating these microparticles or groups of microparticles. This method permits manipulation of microparticles with a plurality of trapping laser beams not mutually interfering just as with two human hands. By coaxially introducing an excited laser beam, it is possible to induce chemical reactions for processing or assembling.