A waveform display apparatus which acquires data from a plurality of channels, and displays information relating to the acquired data in the form of a waveform based on the result of a mathematical operation performed in accordance with a user-entered mathematical expression, wherein at least one mathematical expression is entered and the data output from the plurality of channels are sampled (S01), the entered mathematical expression is analyzed (S02), the at least one mathematical expression is applied to the digital data of the plurality of channels based on the analysis (S03), and the information relating to the data is displayed in the form of a waveform on a display unit based on the result of the mathematical operation (S04). In this way, the user can have the result of the mathematical operation displayed in the desired manner, without having to add a new data processing method each time a necessary operation is added.