A hematological analyzer for measuring blood, sets a body fluid measurement mode; receives a measurement start instruction; irradiates a measurement sample with light and obtains optical information from cells contained in the measurement sample; and classifies at least white blood cells and nucleated cells other than white blood cells contained in the measurement sample, and counts the white blood cells and nucleated cells other than white blood cells based on the optical information obtained from the cells in the measurement sample prepared from a body fluid sample and white blood cell measuring reagent when the body fluid measurement mode has been set and the measurement start instruction has been selected, is disclosed. A method for analyzing body fluid and a computer program product are also disclosed.