A filter controlling expression derivation method comprising: a preparation step of preparing a Fabry-Perot interference filter of which distance between a fixed mirror portion and a movable mirror portion is controlled by balancing an electrostatic force generated between the fixed mirror portion and the movable mirror portion and an elastic force generated in the movable mirror portion at a time of applying a voltage; a first derivation step of deriving a relational expression between a deflection amount of the movable mirror portion and an elasticity index of the movable mirror portion in which the elasticity index of the movable mirror portion is described as a quadratic or higher-order polynomial with the deflection amount of the movable mirror portion as a variable by performing predetermined measurement on the prepared Fabry-Perot interference filter under a predetermined environment temperature, wherein the deflection amount is a distance moved by the movable mirror portion and wherein the elasticity index indicates deflection resistance of the movable mirror portion represented by a virtual spring with a spring constant, wherein the elasticity index is proportional to the spring constant; and a second derivation step of deriving a relational expression between a transmission wavelength of light transmitted through the Fabry-Perot interference filter and the voltage as a filter controlling expression based on the relational expression between the deflection amount and the elasticity index and a relational expression between the electrostatic force and the elastic force, wherein, in the first derivation step, as the predetermined measurement, the transmission wavelength of light transmitted through the Fabry-Perot interference filter is measured in a state where each of a plurality of different voltages is applied as the voltage. a preparation step of preparing a Fabry-Perot interference filter of which distance between a fixed mirror portion and a movable mirror portion is controlled by balancing an electrostatic force generated between the fixed mirror portion and the movable mirror portion and an elastic force generated in the movable mirror portion at a time of applying a voltage; a first derivation step of deriving a relational expression between a deflection amount of the movable mirror portion and an elasticity index of the movable mirror portion in which the elasticity index of the movable mirror portion is described as a quadratic or higher-order polynomial with the deflection amount of the movable mirror portion as a variable by performing predetermined measurement on the prepared Fabry-Perot interference filter under a predetermined environment temperature, wherein the deflection amount is a distance moved by the movable mirror portion and wherein the elasticity index indicates deflection resistance of the movable mirror portion represented by a virtual spring with a spring constant, wherein the elasticity index is proportional to the spring constant; and a second derivation step of deriving a relational expression between a transmission wavelength of light transmitted through the Fabry-Perot interference filter and the voltage as a filter controlling expression based on the relational expression between the deflection amount and the elasticity index and a relational expression between the electrostatic force and the elastic force, wherein, in the first derivation step, as the predetermined measurement, the transmission wavelength of light transmitted through the Fabry-Perot interference filter is measured in a state where each of a plurality of different voltages is applied as the voltage.