Rotation angle detecting device

A rotation angle detecting device includes a resolver (1) that outputs three-phase signals (Va to Vc) based on a rotation angle of a rotary shaft (3), and an R/D converter (2) that acquires the three-phase output signals (Va to Vc) via signal lines (W2a to W2c) corresponding to the respective phases. The R/D converter (2) determines the rotation angle of the rotary shaft (3) on the basis of the three-phase output signals (Va to Vc). The R/D converter (2) includes switching elements (SW1, SW2) that change the potential of the first-phase signal line (W2a) and the potential of the second-phase signal line (W2b), respectively.