AbstractThe purpose of this paper is to study the objective evaluation of educational video software, etc., by biological data. A visual stimulus is presented using CRT, the pupil size and EEG are examined simultaneously, and the changes are analyzed. In such a simultaneous measurement, the interference of CRT noise to EEG measurement must be avoided. A special shielding room is designed using a transparent shielding glass so that the stimulus can be presented to a subject from the outside. The effectiveness of the shielding is verified. The effect of attaching the pupil‐size measuring instrument exerted on EEG measurement is examined. A still‐picture pattern with semantics is presented to the subject while adjusting the average brightness to a constant value, and the pupil size and EEG are measured simultaneously. A negative correlation is observed between the EEG power in the 9.0‐ to 11.0‐Hz band and the pupil size. It is seen also that, when a pattern that strongly interests the subject is presented, the pupil size becomes large and the band power becomes low. Thus, it is demonstrated that the difference of the content of the presented pattern can be evaluated more clearly by the simultaneous measurement.