In this paper, we report the development of a monolithic methanol concentration sensor. An interdigital capacitor and a resonator are fabricated on a single-crystal substrate. The methanol concentration can be measured by measuring the frequency shift of the resonator because the shift corresponds to a change in the relative permittivity of the capacitor connected in series to the resonator. The quality factor (Q) of the sensor is more than 20,000 since the methanol solution is not in contact with the resonator but with the capacitor. The smallest resonator diameter and sensor size for achieving a resolution of 0.3 wt% were 1.5mm and 2.6 × 10.9 × 0.1mm3, respectively. Because the structure and manufacturing process are simple, the proposed sensor can be expected to be used for various kinds of liquid sensing applications. © 2013 The Japan Society of Applied Physics.