The invention discloses a field microwave treatment device for harvested muskmelons. The device comprises a bottom plate, a microwave cavity cover and microwave generators; the bottom plate is used for placing the harvested muskmelons; the microwave cavity cover is buckled on the bottom plate and forms a closed cavity with the bottom plate; a plurality of microwave generators are arranged on eachinner surface of the microwave cavity cover; each microwave generator is used to emit microwaves and apply microwaves to the muskmelons; each microwave generator is made to work intermittently; and the microwave treatment is completed when the temperature inside a 0 to 10 mm thick outer skin layer of the muskmelons reaches 45 to 50 DEG C. The invention further discloses a field microwave treatmentmethod using the field microwave treatment device for the harvested muskmelons; the field microwave treatment device and method for the harvested muskmelons are capable of suppressing pathogenic microorganisms hidden and infiltrated on the muskmelon surface and skin layer, reducing the rot and deterioration of the muskmelons during storage and transportation, and extending the storage and shelf life of the muskmelons.