A flow-rate measurement device includes a first transducer and a second transducer which are provided in a fluid flow path to transmit and receive an ultrasonic signal, a timer unit which measures a propagation time of the ultrasonic signal propagating between the first transducer and the second transducer, and a flow-rate calculation unit which executes a unit measurement step a predetermined number of times and calculates a flow rate of a fluid flowing in the fluid flow path on the basis of the propagation times measured the predetermined number of times, the unit measurement step being an operation in which a direction of transmission to reception between the first transducer and the second transducer is switched and the timer unit measures the propagation times of the ultrasonic signal in both directions. The flow-rate calculation unit measures a flow rate value of the fluid by a precise measurement step in which the unit measurement step is executed a plural number of times to calculate the flow-rate and an exploratory measurement step in which the unit measurement step is executed a smaller number of times than the number of executions in the precise measurement step to calculate the flow rate.