1. A blood analyzer comprising: a dispensing portion configured to dispense a first blood specimen and a second blood specimen from a blood specimen; a sample preparation portion configured to prepare a first measurement sample from the first blood specimen dispensed by the dispensing portion, a first fluorescent dye for staining nucleic acid, and a first hemolyzing agent containing a cationic surfactant, and configured to prepare a second measurement sample from the second blood specimen dispensed by the dispensing portion, a second fluorescent dye for staining nucleic acid, and a second hemolyzing agent not containing a cationic surfactant but containing another surfactant; a light source configured to irradiate light onto each of the first measurement sample and the second measurement sample prepared by the sample preparation portion; a light-receiving portion configured to receive a first fluorescence and a first scattered light from the first measurement sample irradiated with light by the light source and output a first fluorescence signal relating to the received first fluorescence and a first scattered light signal relating to the received first scattered light, and configured to receive a second fluorescence, a second scattered light and a third scattered light from the second measurement sample irradiated with light by the light source and output a second fluorescence signal relating to the received second fluorescence, a second scattered light signal relating to the received second scattered light and a third scattered light signal relating to the received third scattered light; an information processing portion configured to distinguishably detect an atypical lymphocyte, an abnormal lymphocyte and a blast from the blood specimen based on the first fluorescence signal, the first scattered light signal, the second fluorescence signal, the second scattered light signal and a third scattered light signal; and an output portion configured to output a result of the detection made by the information processing portion, the information processing portion distinguishably detecting the abnormal lymphocyte based on the second fluorescence signal, and the information processing portion distinguishably detecting the blast based on the second scattered light signal and the third scattered light signal.