A quartz tuning fork (QTF) has a unique geometry comprising two vibrating prongs separated by a specific gap. The symmetry of the two prongs reduces the number of possible vibration modes, which endows the QTF with a good quality factor. The high stability and low power consumption of QTFs allow them to be used in a wide range of applications, including in precision watches and force sensors. In addition to these conventional applications, there have been attempts to use QTFs as versatile gas sensors because the resonance frequency of a QTF decreases with increasing mass loading. However, the poor mass sensitivity of a typical 32.768 kHz bare QTF (50 ng/Hz) limits its broader applicability in gas sensors. We addressed this problem by attaching a polymer wire or membrane to the two prongs of a QTF. In this configuration, the polymer wire/membrane is stretched and compressed by the two vibrating prongs; the change in the mechanical force of the polymer due to gas adsorption is easily measured from the change in the resonance frequency. We fabricated various polymer wires and membranes and examined the polymer-coated QTF as a gas sensor. Upon exposure to solvent vapor, the resonance frequency of the polymer-coated QTF decreased due to the decrease in the modulus of the polymer wire, which was induced by the adsorption of solvent. Various methods will be discussed in this presentation for the sensitivity enhancement of the polymer-coated QTF.