This study was performed in order to evaluate the irradiative effect of Nd: YAG laser on surface anesthesia. Eleven students at Tsurumi University School of Dental Medicine participated in this study as subjects. Experimental sites were gingivobuccal areas of mandibular canines. The right area was irradiation site, and the left area was control site without irradiation. A pulsed Nd: YAG laser was applied to the areas coated with indian ink, twice for 30 seconds, using 120mJ pulses at 10pps. The judgement of the effect was made through the measurement of the penetrating distance of 30G catridge needle, and the measurement was performed immediately after the irradiation and after a week. The efficasy of pain was assessed by Visual Analogue Scale (VAS). The mean penetrating distance of needle at the irradiation sites revealed 3.8±1.4mm (Mean±SD) at immediately after the irradiation compared to the control sites 1.7±0.9mm, and in 6 cases needle was inserted into periosteum without pain. There was a significant difference (p<0.01) between the irradiation sites and the control sites. The VAS value revealed 2.7±2.9 at the irradiation sites, and 4.2±2.6 at the control sites. The penetrating distance of needle at the irradiation site after a week revealed 0.6 ± 0.4mm, and at the control sites of 1.6±1.0mm. The anesthetic effect of the irradiation of Nd: YAG laser was lost after a week. It was suggested that the irradiation of Nd: YAG laser has anesthesic effect on gingival surface, and that the effect will disappear within 1 week.