In order to more accurately grasp the state of a pit, an information processing device (4) comprises: a data acquisition unit (60) for acquiring multiple items of measurement data (71) indicating theheight of garbage and generated with each measurement carried out by a height measurement device (13); an event determination unit (61) for determining an event in a pit (21) by comparing first measurement data generated as a result of a previous measurement and second measurement data generated as a result of a subsequent measurement; and an accumulation information generation unit (62) for generating accumulation information (74) indicating the state of garbage accumulated in the pit.