The invention is about an ultrasonic welding-based microfluidic device. It is mainly made of a first element and a second element welded one to the other via at least one structure (10, 10′). The structure (10, 10′) comprises an elongated welded portion for said welding, a welding channel (12, 12′) extending between the first and second elements and along one side of the welded portion, and a draining channel (13) communicating with the welding channel (12, 12′) and the microfluidic path (20, 20′) of the device. The invention is further about a method of manufacturing such a device.