Provided is a fluid viscosity measuring device including a support structure having an opening part, the opening part penetrating the support structure in a first direction, a driving resonator fixed to the support structure and extending to overlap the opening part, and a detection resonator fixed to the support structure and extending parallel to the driving resonator, the detection resonator being spaced apart from the driving resonator in the first direction. The driving resonator includes a first piezoelectric body. The detection resonator includes a second piezoelectric body. The first piezoelectric body and the second piezoelectric body have the same shape.