This report proposes a method to improve the position measurement accuracy encoded laser beam scanning type signal field. This signal field system is effective in measurement at small semi-opened field. However, the position measured value is discrete, because this measurement system used M-sequence code consists of 1 and 0. In this research, we proposed to make conventional discrete value linear by instrumentation of phase shift value on the observed signal. First, the principle of encoded laser beam scanning type signal field is referred, and position measurement accuracy is mentioned. Next, a method of high resolution measurement system is proposed, and the effect of this method is confirmed by a experiment using the system we designed.