A signal processing circuit has two types of filters: an IIR filter 11 and an FIR filter 12 having an equivalent transfer function at all times. In an adjustment mode in which the signal processing circuit is adjusted to have an arbitrary transfer function, the signal processing circuit makes a configuration setting to use the IIR filter 11. When completing the adjustment or in a signal processing mode, the signal processing circuit makes a configuration setting change to switch to the FIR filter 12 having the equivalent transfer function.