<p>Steel sheet piles used in drainage canal walls are highly susceptible to corrosion, which leads to a reduction in their thickness over time. Thickness loss is conventionally measured using ultrasonic testing, spot-based and contact-type measurement. This measurement is time-consuming and labor-intensive, especially for long drainage canals with numerous measurement points. In this study, we propose a non-contact method for detecting the thickness of corroded steel sheet piles using infrared thermography (IRT), which enables efficient multi-point measurement. Our proposed method estimates the thickness of steel sheet piles based on the principle that thinner materials with lower heat capacity more rapidly change their temperature. Thermal images were used to measure the surface temperature of two in-service steel sheet piles. The relationship between surface temperature and thickness is analyzed using a heat balance model, which draws insights from ground heat exchange principles. Additionally, ordinary kriging is employed to reduce noise in the thermal images. The results demonstrate that the measured temperatures closely align with the values predicted by the heat balance model after noise reduction. This study introduces a novel non-contact method for thickness detection, expecting to offer an efficient and rapid approach for evaluating the condition of aging steel structures.</p>