The purpose of this study was to examine the output energy changes of the contact probe for Er:YAG laser with tooth ablation and evaluate the effect of contact surface polishing on output energy. The Er:YAG laser was irradiated to enamel of extracted human incisors for 100min (5min×20times). The output energy of contact probes was measured every 5min (n=3). After 100min, the contact surfaces were polished using silicon carbide paper up to #1500, and the output energy of the probe was measured. The contact surfaces of the probes were observed and analyzed using an EPMA. After 100min, the output energy showed 49.4% of the energy of an unused probe. After the contact surfaces were polished to #1500, the output energy returned to 96.4% of baseline. It is suggested that the output energy of the contact probe decreased with tooth ablation, and polishing of the contact surface was effective to regain the energy.