This blood analyzer includes a sample preparation portion preparing a measurement sample containing no labeling substance from a blood sample and a hemolytic agent containing no labeling substance, a light information generation portion generating fluorescent information and at least two types of scattered light information from the measurement sample and a control portion performing a first classification of white blood cells in the measurement sample into at least four groups of monocytes, neutrophils, eosinophils and a group of the others on the basis of the fluorescent information and the two types of scattered light information.