In a measurement unit, a primary acceleration sensor is fixed at the center of gravity of a flying object or at a position within a certain error range from the center of gravity. A secondary acceleration sensor is fixed inside the flying object so as to be spaced from the center of gravity of the flying object. In a measurement apparatus, an acquirer acquires a primary acceleration measured by the primary acceleration sensor during flight of the flying object and a secondary acceleration measured by the secondary acceleration sensor during the flight of the flying object. An estimator estimates a spin rate per unit time of the flying object from the acquired primary acceleration and the acquired secondary acceleration using maximum likelihood estimation.