A method for inspecting susceptibility of bacteria or fungi to an antimicrobial drug using a micro-device having a plurality of flow channels, the method comprising: an incubating step of incubating a mixture of the antimicrobial drug and a bacterial suspension or fungal suspension to be inspected in the plurality of flow channels of the micro-device; and a detecting step of detecting, with a microscope, bacteria or fungi derived from the bacterial suspension or fungal suspension to be inspected in each of observation areas of the plurality of flow channels of the micro-device, wherein in the micro-device: (i) the antimicrobial drug is previously placed in each of the plurality of flow channels; (ii) the plurality of flow channels have a common inlet; (iii) each of the flow channels comprises the common inlet, the observation area, and an exhaust section in this order; (iv) the observation areas of the plurality of flow channels are converged and placed in parallel so as to be in a field of the microscope; (v) the observation areas of the plurality of flow channels all have the same width and the same length; (vi) in each of the flow channels, a part extending from an exhaust-section side end of the observation area to the exhaust section is shorter than a part extending from a common inlet-side end of the observation to the common inlet; and (vii) the bacterial suspension or fungal suspension to be inspected is introduced into the plurality of flow channels via the common inlet of the micro-device before the incubating step or in the incubating step. an incubating step of incubating a mixture of the antimicrobial drug and a bacterial suspension or fungal suspension to be inspected in the plurality of flow channels of the micro-device; and a detecting step of detecting, with a microscope, bacteria or fungi derived from the bacterial suspension or fungal suspension to be inspected in each of observation areas of the plurality of flow channels of the micro-device, wherein in the micro-device: (i) the antimicrobial drug is previously placed in each of the plurality of flow channels; (ii) the plurality of flow channels have a common inlet; (iii) each of the flow channels comprises the common inlet, the observation area, and an exhaust section in this order; (iv) the observation areas of the plurality of flow channels are converged and placed in parallel so as to be in a field of the microscope; (v) the observation areas of the plurality of flow channels all have the same width and the same length; (vi) in each of the flow channels, a part extending from an exhaust-section side end of the observation area to the exhaust section is shorter than a part extending from a common inlet-side end of the observation to the common inlet; and (vii) the bacterial suspension or fungal suspension to be inspected is introduced into the plurality of flow channels via the common inlet of the micro-device before the incubating step or in the incubating step. (i) the antimicrobial drug is previously placed in each of the plurality of flow channels; (ii) the plurality of flow channels have a common inlet; (iii) each of the flow channels comprises the common inlet, the observation area, and an exhaust section in this order; (iv) the observation areas of the plurality of flow channels are converged and placed in parallel so as to be in a field of the microscope; (v) the observation areas of the plurality of flow channels all have the same width and the same length; (vi) in each of the flow channels, a part extending from an exhaust-section side end of the observation area to the exhaust section is shorter than a part extending from a common inlet-side end of the observation to the common inlet; and (vii) the bacterial suspension or fungal suspension to be inspected is introduced into the plurality of flow channels via the common inlet of the micro-device before the incubating step or in the incubating step.