A physical quantity measuring apparatus includes an oscillation drive circuit that forms an oscillation loop together with a physical quantity transducer and excites a drive oscillation of the physical quantity transducer, and a detection circuit that detects an analog detection signal outputted from the physical quantity transducer using a detection circuit first and thence converts the signal that has been detected into a digital signal using an A/D converter to output the digital signal. The oscillation drive circuit has a drive amplitude detection circuit that detects amplitude of the drive oscillation. A voltage level of a reference of the A/D converter included in the detection circuit is controlled on the basis of a detection output signal of the drive amplitude detection circuit.