Laser printers are widely used in modern society, and VOCs and ultrafine particles emitted from printers have been known to cause adverse effects on indoor environment. In this study we conducted experiments in order to evaluate the ultrafine particles emission characteristics of laser printers and to reduce its concentration. Ultrafine particles emission characteristics was assessed for 15 printers by measuring its number concentration inside the printers (before and after the fuser) while printing. In addition, chemical analysis was performed using transmission electron microscope (TEM), Matrix-assisted laser desorption ionization time of flight mass spectroscopy (MALDI-TOF MS) and gel permeation chromatography (GPC). In order to reduce the occurrence of ultrafine particles from laser printers, an experiment was conducted with lowered fusing temperature, which resulted in the sharp decrease of the ultrafine particles generation due to the decrease in particle nucleation rate. Additionally, based on the fact that ultrafine particles contains paramagnetic material, by applying electromagnetic field, ultrafine particles emitted from laser printer was reduced by similar to 40%.