BACKGROUND Recently, a stag beetle (SB) knife was introduced to reduce the difficulty of peroral endoscopic myotomy (POEM). The objective of this study was to evaluate the efficacy and safety of the SB knife. MATERIAL AND METHODS A total of 71 patients undergoing POEM with the SB knife for esophageal achalasia were included. We used esophagography, manometry, esophagogastroduodenoscopy (EGD), and Eckardt score to assess the utility and safety. RESULTS All cases were completed for POEM. The incidence of adverse events during the operation were 2.8%; however, all cases were treated conservatively. There was a vast improvement in clinical symptoms and endoscopic findings. The average Eckardt score was 6.9 before and 0.6 at 1 year after POEM (p<0.05). The average lower esophageal sphincter (LES) pressure before and 6 months after POEM were 44.34±14.83 mmHg and 19.14±6.74 mmHg (p<0.05), respectively. The average LES relaxation pressure before and 6 months after POEM was 12.11±5.02 mmHg and 3.22±2.29 mmHg (p<0.05), respectively. CONCLUSIONS POEM with the SB Knife is technically efficient and safe in treating achalasia and is associated with favorable short-term outcomes.