A pain estimation apparatus for estimating a magnitude of pain of an object being estimated based on a brainwave of the object being estimated, comprising: a measurement unit for measuring a brainwave a plurality of times from the object being estimated to obtain a plurality of brainwave data or analysis data thereof, wherein the brainwave data or analysis data thereof comprises an amplitude of the brainwave data; and an estimation unit for estimating a relative magnitude of pain upon the measurement of a brainwave a plurality of times from the plurality of brainwave data or analysis data thereof, based on a pain function for a relationship between the amplitude of the brainwave data and pain, wherein the pain function comprises a sigmoid function, wherein the plurality of brainwave data or analysis data thereof comprise first brainwave data or analysis data thereof and second brainwave data or analysis data thereof, and wherein the estimation unit (i) is configured to estimate that first pain corresponding to the first brainwave data or analysis data thereof is greater than second pain corresponding to the second brainwave data or analysis data thereof if the amplitude of the first brainwave data is greater than the amplitude of the second brainwave data, and (ii) is configured to estimate that the first pain is less than the second pain if the amplitude of the first brainwave data is less than the amplitude of the second brainwave data. a measurement unit for measuring a brainwave a plurality of times from the object being estimated to obtain a plurality of brainwave data or analysis data thereof, wherein the brainwave data or analysis data thereof comprises an amplitude of the brainwave data; and an estimation unit for estimating a relative magnitude of pain upon the measurement of a brainwave a plurality of times from the plurality of brainwave data or analysis data thereof, based on a pain function for a relationship between the amplitude of the brainwave data and pain, wherein the pain function comprises a sigmoid function, wherein the plurality of brainwave data or analysis data thereof comprise first brainwave data or analysis data thereof and second brainwave data or analysis data thereof, and wherein the estimation unit (i) is configured to estimate that first pain corresponding to the first brainwave data or analysis data thereof is greater than second pain corresponding to the second brainwave data or analysis data thereof if the amplitude of the first brainwave data is greater than the amplitude of the second brainwave data, and (ii) is configured to estimate that the first pain is less than the second pain if the amplitude of the first brainwave data is less than the amplitude of the second brainwave data. (i) is configured to estimate that first pain corresponding to the first brainwave data or analysis data thereof is greater than second pain corresponding to the second brainwave data or analysis data thereof if the amplitude of the first brainwave data is greater than the amplitude of the second brainwave data, and (ii) is configured to estimate that the first pain is less than the second pain if the amplitude of the first brainwave data is less than the amplitude of the second brainwave data.