1. A load calculating device comprising: 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, wherein one or more electronic components are mounted on the circuit board; a first storage configured to store a first statistical model that is one of; a regression model determining an intermediate variable from the monitoring variables, an occurrence frequency distribution relating to the monitoring variables and the intermediate variable, and a probability distribution relating to the monitoring variables and the intermediate variable; a second storage configured to store, for at least one place on the circuit board, a second statistical model that is one of: a regression model determining a physical quantity from the intermediate variable, an occurrence frequency distribution relating to the intermediate variable and the physical quantity, and a probability distribution relating to the intermediate variable and the physical quantity; 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 on the at least one place from the calculated intermediate variable according to the second statistical model, wherein the intermediate variable is a variable which expresses a different physical quantity than the physical quantity calculated according to the second statistical model and is not monitored by the monitor or the tool.