System for diagnosing oil properties in working machine

The present invention is provided with: a storage device (210) in which sensor information (A) inputted from a sensor (101A) that detects the oil properties of oil used in the operation of a working machine, and an abnormality degree determination value determined per sensor information (A) are stored; and an arithmetic processing device (104) that executes a first process for determining a degree of abnormality of the oil on the basis of the sensor information (A) and the abnormality degree determination value, a second process for determining whether or not it is necessary to perform oil analysis involving oil collection, on the basis of the degree of abnormality of the oil determined in the first process, and a third process for, when it is determined in the second process that the oil analysis is necessary, outputting such determination to another terminal.