The invention provides an abnormal operation detection device estimating an overload operation of a hydraulic shovel on the basis of an amount of hydraulic operation. An accumulated amount of an operation amount is calculated by an accumulated amount calculating means on the basis of an operation amount of each of operation mechanisms obtained by an operation pressure detecting means, an operation fluctuation amount is calculated by a fluctuation amount calculating means, a joint angle of each of the operation mechanisms is estimated on the basis of the accumulated amount, and an overload operation is determined by using an abnormal operation determining means on the basis of the estimated joint angle and the operation fluctuation amount.