<;P>;PROBLEM TO BE SOLVED: To provide a method for suppressing infectivity by sterilizing or inactivating microbes without deteriorating or damaging blood. <;P>;SOLUTION: An apparatus for treating microbes comprises an infrared laser oscillator, a wave length converter for the generated infrared laser, and a beam splitter for selecting laser ray of a predetermined wave length from the wave length converted laser light and constituted to sterilize or inactivate the microbes by irradiating the microbes with the laser ray having a predetermined wave length. <;P>;COPYRIGHT: (C)2005,JPO&NCIPI