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 fluorescence and a scattered light from the first measurement sample irradiated with light by the light source and output a first fluorescence signal relating to the received fluorescence and a first scattered light signal relating to the received scattered light, and configured to receive a fluorescence and a scattered light from the second measurement sample irradiated with light by the light source and output a second fluorescence signal relating to the received fluorescence and a second scattered light signal relating to the received 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 and the second scattered light signal; and an output portion configured to output a result of the detection made by the information processing portion.