A testing method using a micro flow path device configured for a test liquid containing a specimen to be brought into contact with a drug therein and for a test on an action of the drug on the specimen includes: preparing the micro flow path device including: a plurality of micro flow paths, first and second openings which are disposed at both ends of each of the plurality of micro flow paths and communicate with an outside, a storage unit which is provided in each of the plurality of micro flow paths and stores the drug, and a gas-permeable membrane covering the first opening; applying a fluid pressure higher than an external pressure to the test liquid through the second opening from a syringe pump connected to the second opening to pressure-feed the test liquid to the storage unit; and observing a target region set in the micro flow path.