Strain gauges are widely used in Structural Health Monitoring (SHM) systems because they are inexpensive, easy to install, and sensitive enough to detect the potential danger of collapse of a building or structure. However, off-the-shelf equipment for the strain gauges is usually either wired to the sensors or wireless with very limited range, which significantly increases the total cost as well as restricting the performance of the deployment. In this paper, we propose a structural health monitoring system based on wireless sensor nodes equipped with inexpensive strain gauges. The performance of the system is not limited, because multi-hop deployment is possible. Our system consists of a sensor board, which properly amplifies and converts the signal from the strain gauges, and communication software, written in TinyOS, that is in charge of reliable transport of the strain data. We evaluated our system in comparison with the commercial equipment. The experiment results show that the proposed system is reliable and effective for use in structural health monitoring.