A signal processing apparatus for performing signal processing including a plurality of steps in data units by software signal processing includes signal processing modules performing the steps, a circuit configuration information storing and managing unit storing the signal processing modules and circuit configuration information, a signal processing order determining unit determining a signal processing order by performing path routing, a signal processing executing unit executing the signal processing in the determined order, and a circuit configuration changing unit changing circuit configuration information and causing the signal processing order determining unit to re-execute path routing to determine a signal processing order for the changed circuit configuration information during a period from the end of the software signal processing in the data unit to the beginning of the subsequent data unit. Software signal processing from the beginning of the subsequent data unit is performed with the changed circuit configuration.