An information processing device for monitoring waste deposited inside a pit, the information processing device comprising: a data obtaining section configured to obtain a plurality of pieces of measurement data that is generated by a height measuring device each time the height measuring device carries out measurement and that indicates a height of the waste, wherein the height measuring device is a three-dimensional measurement device for measuring a surface shape of the waste deposited inside the pit, the information processing device further comprises: an event determining section configured to compare (i) first measurement data generated as a result of previous measurement with (ii) second measurement data generated as a result of later measurement, both the first measurement data and the second measurement data being in a form of three-dimensional measurement data indicative of a shape of the waste, determine one or more sets of XY-coordinate values as one or more respective height change areas in the pit at each of which one or more sets the height of the waste which height is indicated with a Z-coordinate value has been changed by not less than a predetermined value, determine an event related to movement of the waste that occurred in each of the one or more determined height change areas; and a deposition information generating section configured to, on a basis of the event determined, generate deposition information indicative of a state of how the waste deposited inside the pit has been stirred. a data obtaining section configured to obtain a plurality of pieces of measurement data that is generated by a height measuring device each time the height measuring device carries out measurement and that indicates a height of the waste, wherein the height measuring device is a three-dimensional measurement device for measuring a surface shape of the waste deposited inside the pit, the information processing device further comprises: an event determining section configured to compare (i) first measurement data generated as a result of previous measurement with (ii) second measurement data generated as a result of later measurement, both the first measurement data and the second measurement data being in a form of three-dimensional measurement data indicative of a shape of the waste, determine one or more sets of XY-coordinate values as one or more respective height change areas in the pit at each of which one or more sets the height of the waste which height is indicated with a Z-coordinate value has been changed by not less than a predetermined value, determine an event related to movement of the waste that occurred in each of the one or more determined height change areas; and a deposition information generating section configured to, on a basis of the event determined, generate deposition information indicative of a state of how the waste deposited inside the pit has been stirred. an event determining section configured to compare (i) first measurement data generated as a result of previous measurement with (ii) second measurement data generated as a result of later measurement, both the first measurement data and the second measurement data being in a form of three-dimensional measurement data indicative of a shape of the waste, determine one or more sets of XY-coordinate values as one or more respective height change areas in the pit at each of which one or more sets the height of the waste which height is indicated with a Z-coordinate value has been changed by not less than a predetermined value, determine an event related to movement of the waste that occurred in each of the one or more determined height change areas; and compare (i) first measurement data generated as a result of previous measurement with (ii) second measurement data generated as a result of later measurement, both the first measurement data and the second measurement data being in a form of three-dimensional measurement data indicative of a shape of the waste, determine one or more sets of XY-coordinate values as one or more respective height change areas in the pit at each of which one or more sets the height of the waste which height is indicated with a Z-coordinate value has been changed by not less than a predetermined value, determine an event related to movement of the waste that occurred in each of the one or more determined height change areas; and a deposition information generating section configured to, on a basis of the event determined, generate deposition information indicative of a state of how the waste deposited inside the pit has been stirred.