This study was conducted to investigate the effect of experimental warming on soil CO₂ concentration in Quercus variabilis and Pinus densilfora seedlings. Sixty four Q. variabilis and ninety P. densiflora seedlings were each planted in 1 m × 1 m plots (n=4) in April 2010 and stem density was controlled in March 2011 and March 2012. The air temperature in warmed plots was increased by 3°C compared to control plots using the infrared lamp from November 2010. Soil CO₂ concentration at 5 cm depth soil and soil temperature were continuously measured by using the CO₂ sensors (GMT222, Vaisala CARBOCAP, Finland) and temperature sensors (107-L34, Campbell Scientific Inc., USA). There was no significant difference in mean soil CO₂ concentration between control and warmed plots and the values (ppm) ranged from 907 to 13,153 in Q. variabilis and from 813 to 11,383 in P. densiflora, respectively. Soil CO₂ concentration was correlated with soil temperature in control and warmed plots. Q10 values in control and warmed plots were 1.67 and 1.35 for Q. variabilis, and 1.55 and 1.47 for P. densiflora in 2012, respectively.