This study was to find the best adhesive condition comparing mechanical property in case of hot-melt adhesion using glue-gun, ultrasonic welding with adhesion and only ultrasonic welding in order to adhere thermoplastic resin of polyethylene (PE) in which reliable adhesion was resulted in case of ultrasonic welding with same materials of PE. The best welding condition were acquired at welding time 1 second, welding pressure 250kPa for PE-PE where welding time and welding pressure were increased in accordance with the increase of material strength. At the best ultrasonic welding conditions, bonding strength of PE-PE welding was about 21MPa of which material have tensile strength of 24MPa. Through the analysis of microscophic test for ultrasonic welding structure, it was distinguished between well welded structure with higher intermolecule flow and bad welded structure with lower flow, of which result is mostly correspond with the result of tensile strength test.