A tracing apparatus that is connected to a PLC for inputting and outputting signals based on a ladder program includes: a ladder program analysis unit that analyzes an order in which nets in the ladder program are arranged so as to produce an execution order signal table indicating an order in which the nets are executed; a trace target setting unit that sets one or more nets to be traced; a trace data acquisition unit that acquires trace data in a predetermined sampling cycle; a compensation determination unit that determines, based on the table, whether or not the state (reference signal) of a signal at a contact included in a ladder circuit to be traced needs to be compensated for; and an output unit that outputs a ladder diagram of a trace result which has been compensated for based on the result of the determination of the compensation determination unit.