The detecting apparatus according to the present disclosure comprises devices each including an artificial cell wall, a test sample inlet provided above the artificial cell wall, and a culture medium layer provided under the artificial cell wall, and an observation part configured to laterally observe at least one of the culture medium layers of the devices, wherein the culture medium layers of the devises respectively contain different technical-grade active ingredients, each of the culture medium layers of the devices includes a plurality of layers that each contain an agricultural chemical in a standard amount or at a diluted concentration with respect to the standard amount and are stacked in a descending order of concentration of the agricultural chemical from bottom to top, and each of the culture medium layers of the devices further includes, as an uppermost layer, a layer containing no agricultural chemical.