ESD is a technically difficult and time-consuming procedure for the treatment of large colorectal tumors. In Japan, Ball-Tip Bipolar Current Needle Knife (BB-knife) has been used as a device for safe treatment in ESD by minimizing the damage in deeper tissues of colorectal neoplasms. In May 2012, a BB-knife combined with Water-Jet function (Jet B-knife) was newly developed. The aim of this study was to examine the effectiveness and safety of Jet B-knife, which is the Bipolar Current Needle Knife with a ball tip and 1.5 mm in length. The endoscope we used was Olympus H260AZI or PCF260AI. Electorosurgical unit was VIO300D(ERBE) with dry cut mode (effect 3,60W) or spray coagulation mode (effect 2 60W). Translucent hood had been always attached to the point of the endoscope. We treated 276 lesions by ESD using BB-knife between March 2007 and April 2012(group A) and 245 lesions using Jet B-knife between May 2012 and March 2016 (group B). We retrospectively evaluated including the diameter of resected tumor, the time required for resection, the rate of en-block complete resection, the rate of perforation, and compare these data between two groups. The median time required for the resection was 103 min. in group A and 51 min. in group B. The difference was statistically significant (p<0.01). And the median diameter of tumor in group A was 23.1mm and that in group B was 26.2mm. The difference was statistically significant (p<0.01). On the other hand, the en-block complete resection rate was 94% in group A and 98% in group B. The rate of perforation was 1.8% in group A and 1.6% in group B. These differences were not statistically significant. The resection time was significantly shortened using Jet B-knife, although the mean size of lesions was significantly larger than the other. This may be not only due to the improvement of cutting skill but also due to the efficient water jet function during the procedure of hemostasis and the enhanced lifting effects of lesions by launching it at the submucosal layer. Collectively, the use of Jet B-knife may contribute to time-saving and safe procedure in ESD for the colorectal tumors.