First and second ΔΣ modulators convert output signals of two sensors into pulse density signals. First and second LPFs convert the pulse density signals into multi-bit signals. A signal computing module calculates a mass flow rate based on the multi-bit signals. A resonance circuit generates an excitation signal based on the output signals of the sensors. A drive output module amplifies the excitation signal. An exciter excites the measurement tube using an amplified excitation signal. A multiplier amplifies one of the pulse density signals to generate a multi-bit signal. An amplification factor controller controls an amplification factor of the multiplier based on the multi-bit signal. A third ΔΣ modulator converts an amplified signal into a pulse density signal. A DAC generates the excitation signal based on the pulse density signal.