A reusable immunosensor that employed surface acoustic wave (SAW) was developed for monitoring of physiological information. The SAW immunosensor was fabricated by modifying a propagation area of the SAW device with a self-assembled monolayer of pH tolerant protein, ORLA85, which allowed repeating of surface regeneration by changing pH, and thereby rapid and repetitive (semi-continuous) measurement of analyte concentration. In experiment, initially a SAW device used for the sensor was characterized using a series of solution with various viscosity, and results showed a good correlation between phase change and solution viscosity from 0.88 to 1.7 mPa-s. In addition, performance of developed SAW immunosensor was evaluated using mouse IgG and anti-mouse IgG as model capturing molecule and analyte. It revealed that dynamic range of the immunosensor was 0.16-100 μg/mL with a measurement time of 20 minutes, and semi-continuous measurement was possible with a high reproducibility represented by a coefficient of variation of 3.4% for five repetitive measurement. These demonstrated that SAW immunosensor holds a huge potential for application to monitoring of time course of biomolecules which reflect physiological conditions.