There is provided with a load calculating device including: a variable acquiring unit configured to acquire, as monitoring variables, a detected value by a sensor monitoring a state of a circuit board and a performance characteristic obtained by a tool monitoring performance of the circuit board; a first storage configured to store a first statistical model that is one of a regression model, an occurrence frequency distribution and a probability distribution; a second storage configured to store a second statistical model that is one of a regression model, an occurrence frequency distribution and a probability distribution; and an arithmetic processor configured to calculate the intermediate variable from the monitoring variables acquired by the variable acquiring unit according to the first statistical model and calculate the physical quantity from calculated intermediate variable according to the second statistical model.