Since the increase in the overall mortality rate in patients with colon cancer is remarkably high in recent years, early treatment is required. For this reason, endoscopic submucosal dissection (ESD) has been at the forefront of international attention as a low invasive treatment for early digestive cancer. In current ESD procedure, an electrosurgical knife is used for mucosal incision and subsequent submucosal dissection. However, the perforation has been reported to occur by approximately 5%. Thus, to enhance the tissue selectivity of this modality, we focused on the application of laser for ESD. A carbon dioxide laser was chosen as a surgical knife because the saline or a sodium hyaluronate solution injected into the submucosal layer in current ESD procedure has a high absorption coefficient at the wavelength of the carbon dioxide laser. In this research, ex vivo experiment was performed at the output power of 3–7 W and discuss the optimum irradiation power of laser. As a result of ex vivo experiment using extracted porcine colon tissues, mucosal incision and submucosal dissection were safely and less invasively performed in every output power, without reaching the thermal damage to a muscular layer. This is because a carbon dioxide laser is strongly absorbed by saline injected into submucosa. ESD using a carbon dioxide laser is a safer method for the treatment of early colon cancer. We are planning to measure and compare the optical and thermal properties of porcine colon with those of human colon.