A reducer damage-state notification apparatus for notifying a damage state of a reducer of a machine which includes the reducer and a lubricant deterioration sensor for detecting deterioration of lubricant of the reducer, wherein the machine is formed with an oil accommodation space which is a space capable of accommodating the lubricant, the reducer is formed with an intra-reducer oil-accommodation space as a part of the oil accommodation space, the lubricant deterioration sensor includes: a light emitting element configured to emit light; a color light reception element configured to detect color of received light; and a gap forming member disposed on an optical path from the light emitting element to the color light reception element, the gap forming member forming an oil gap into which the lubricant enters and configured to transmit light therethrough, characterized in that the reducer damage-state notification apparatus comprises: a damage-state notification unit configured to notify the damage state of the reducer; a threshold setting unit configured to set a threshold for performing notification by the damage-state notification unit; and an oil sealing rate acceptance unit configured to accept an input of an oil sealing rate representing a ratio of an amount of the lubricant with respect to a capacity of the intra-reducer oil-accommodation space, wherein the damage-state notification unit is configured to notify the damage state of the reducer corresponding to the threshold when a color difference between the color detected by the color light reception element and a predetermined color reaches the threshold set by the threshold setting unit, and the threshold setting unit is adapted to set the threshold according to the oil sealing rate which input is accepted by the oil sealing rate acceptance unit. a light emitting element configured to emit light; a color light reception element configured to detect color of received light; and a gap forming member disposed on an optical path from the light emitting element to the color light reception element, the gap forming member forming an oil gap into which the lubricant enters and configured to transmit light therethrough, characterized in that the reducer damage-state notification apparatus comprises: a damage-state notification unit configured to notify the damage state of the reducer; a threshold setting unit configured to set a threshold for performing notification by the damage-state notification unit; and an oil sealing rate acceptance unit configured to accept an input of an oil sealing rate representing a ratio of an amount of the lubricant with respect to a capacity of the intra-reducer oil-accommodation space, wherein the damage-state notification unit is configured to notify the damage state of the reducer corresponding to the threshold when a color difference between the color detected by the color light reception element and a predetermined color reaches the threshold set by the threshold setting unit, and the threshold setting unit is adapted to set the threshold according to the oil sealing rate which input is accepted by the oil sealing rate acceptance unit. a damage-state notification unit configured to notify the damage state of the reducer; a threshold setting unit configured to set a threshold for performing notification by the damage-state notification unit; and an oil sealing rate acceptance unit configured to accept an input of an oil sealing rate representing a ratio of an amount of the lubricant with respect to a capacity of the intra-reducer oil-accommodation space, wherein the damage-state notification unit is configured to notify the damage state of the reducer corresponding to the threshold when a color difference between the color detected by the color light reception element and a predetermined color reaches the threshold set by the threshold setting unit, and the threshold setting unit is adapted to set the threshold according to the oil sealing rate which input is accepted by the oil sealing rate acceptance unit.