An apparatus for measuring a hematological sample, comprising: a sample treatment part for preparing a measuring sample by giving damage to a cell membrane of erythrocyte and mature leukocyte contained in the hematological sample, constricting the damaged erythrocyte, and staining the damaged mature leukocyte with a fluorescent dye for staining nucleic acid; a sheath flow cell for flowing the measuring sample; a light source for irradiating light, which includes light having a wavelength which is able to excite the fluorescent dye, to the measuring sample introduced into the sheath flow cell; a forward scattered light detector for obtaining forward scattered light intensity from the irradiated measuring sample; a side scattered light detector for obtaining side scattered light intensity from the irradiated measuring sample; a side fluorescent light detector for obtaining fluorescent intensity from the irradiated measuring sample; and a control part configured for performing operations comprising: specifying a first cell group containing myeloblast based on the forward scattered light intensity and the side scattered light intensity; specifying a second cell group containing myeloblast based on the forward or side scattered light intensity and the fluorescent intensity; and calculating a cell belonging to both of the first and second cell groups as myeloblast, the apparatus is characterized in that the control part is configured for performing further operations comprising: preparing a two-dimensional scattergram having the forward and side scattered light intensities on the two axes; and displaying the first cell group set in the two-dimensional scattergram as a myeloblast appearance candidate region which is discriminated from lymphocyte, monocyte, granulocyte and immature granulocyte. a sample treatment part for preparing a measuring sample by giving damage to a cell membrane of erythrocyte and mature leukocyte contained in the hematological sample, constricting the damaged erythrocyte, and staining the damaged mature leukocyte with a fluorescent dye for staining nucleic acid; a sheath flow cell for flowing the measuring sample; a light source for irradiating light, which includes light having a wavelength which is able to excite the fluorescent dye, to the measuring sample introduced into the sheath flow cell; a forward scattered light detector for obtaining forward scattered light intensity from the irradiated measuring sample; a side scattered light detector for obtaining side scattered light intensity from the irradiated measuring sample; a side fluorescent light detector for obtaining fluorescent intensity from the irradiated measuring sample; and a control part configured for performing operations comprising: specifying a first cell group containing myeloblast based on the forward scattered light intensity and the side scattered light intensity; specifying a second cell group containing myeloblast based on the forward or side scattered light intensity and the fluorescent intensity; and calculating a cell belonging to both of the first and second cell groups as myeloblast, specifying a first cell group containing myeloblast based on the forward scattered light intensity and the side scattered light intensity; specifying a second cell group containing myeloblast based on the forward or side scattered light intensity and the fluorescent intensity; and calculating a cell belonging to both of the first and second cell groups as myeloblast, the apparatus is characterized in that the control part is configured for performing further operations comprising: preparing a two-dimensional scattergram having the forward and side scattered light intensities on the two axes; and displaying the first cell group set in the two-dimensional scattergram as a myeloblast appearance candidate region which is discriminated from lymphocyte, monocyte, granulocyte and immature granulocyte. preparing a two-dimensional scattergram having the forward and side scattered light intensities on the two axes; and displaying the first cell group set in the two-dimensional scattergram as a myeloblast appearance candidate region which is discriminated from lymphocyte, monocyte, granulocyte and immature granulocyte.