A loading weight detection device applicable to various mobile bodies can accurately detect loading weight with minimized number of input variables. It includes a touch panel 33 receiving input of vehicle body weight ma and initial setting cargo weight mb0; an oscillation detection part 20 detecting cargo vehicle oscillation; an arithmetic part 31 functioning as natural vibration identifying means for identifying natural vibration in self-weight direction as vertical oscillation center-of-gravity-specific natural vibration value, based on oscillation data detected by an oscillation detection part 20; a storage part 32 storing vertical oscillation center-of-gravity-specific natural vibration value identified by an arithmetic part 31 with cargo having initial setting cargo weight of mb0 loaded on cargo vehicle, vehicle body weight ma, and initial setting cargo weight mb0 as initial setting data, arithmetic part 31 calculating total weight M, being based on vertical oscillation center-of-gravity-specific natural vibration value identified and initial setting data.