According to one embodiment, an inspection apparatus includes an irradiation device irradiating an inspection target substrate with multiple beams, a detector detecting each of a plurality of charged particle beams formed by charged particles emitted from the inspection target substrate as an electrical signal, and a comparison processing circuitry performing pattern inspection by comparing image data of a pattern formed on the inspection target substrate, the pattern being reconstructed in accordance with the detected electrical signals, and reference image data. The detector includes a plurality of detection elements that accumulate charges, and a detection circuit that reads out the accumulated charges. The plurality of detection elements are grouped into a plurality of groups. The detection circuit operates in a manner of, during a period in which the charged particle beams are applied to the detection elements included in one group, reading out the charges accumulated in the detection elements included in one or more other groups.