PURPOSE: To lyse the cell of arbitrary microorganism or plant, by the catalytic action of a semiconductor utilizing light energy.

CONSTITUTION: Cells of microorganism or plant are floated or suspended in a solution composed mainly of water. The dispersion is added with one or more semiconductors selected from oxides, sulfides, phosphide, arsenides, selenides and tellurides of a metal and particles of catalyst composed of metals such as platinum, palladium, rhodium, etc. and having particle diameter of several hundreds W several thousands . The mixture is irradiated with light having higher energy than the excitation energy of said semiconductor. The cell wall of the microorganism or plant is oxidized and decomposed by the oxidative catalytic action of the catalyst particle.