A blood analyzer comprises a sample preparing part configured to prepare a measurement sample from a blood sample, an staining dye and diluent, a detecting part configured to detect the fluorescent light intensity and the scattered light intensity, an output part, and an analyzing part configured to identify the population including red blood cells infected by ring-form malaria parasite based on the fluorescent light intensity and the scattered light intensity, and output to the output part the information relating to infection of Plasmodium falciparum based on the scattered light distribution of particles associated with the identified population that includes red blood cells infected by the ring-form malaria parasite.