This paper describes the automatized excavating system that was developed for excavating ditches for drains. This system we developed is composed of two sub- systems, an automatic surface finishing system and a laser guided system. The controller calculates the position of the bucket- tip by using information of the laser position and joint angle sensors. Then each proportional solenoid valve is controlled so that the bucket-tip position follows the desired path. Therefore, automatic finishing can be realised just by pushing a start button. Through the field tests, it was proved that this system was able to improve work efficiency to reduce labours and to improve accuracy.