In order to investigate the mechanism in which particulate matter (PM) is discharged from diesel engines, it is necessary to carry out a quantitative analysis of the substances it contains. Paying attention to the calcium content in the PM of a laboratory diesel engine, this research discussed the method of the quantitative analysis conducted, and the mechanism in which it was discharged. The origin of the calcium in PM comes from calcium contained in the lubricating oil of the engine. The calcium in the lubricating oil and in the residual substance of the oil during the evaporation process can be extracted by ultrasonic cleaning with the mobile phase (dilute sulfuric acid) using ion-chromatography. Quantitative analysis of calcium was carried out using ion-chromatography. The same method is used for the quantitative analysis of calcium in dust (JIS Z 8808). The results showed a 0.2 mg/m³N-dry calcium concentration in the exhaust gas of the engine. The rate of lubricating oil consumption was determined to be 0.2 g/kWh from these results. When the lubricating oil is simply heated, the calcium it contains remains the residual substance. Therefore, calcium in the exhaust gas of the engine indicates that a part of the lubricating oil is consumed as oil droplets.