1. A stimulating task presentation device in a living body optical measurement device comprising: a stimulation presenting unit configured to present a stimulation to an examinee; a brain function measuring device configured to measure a brain function of the examinee in parallel to the presentation of the stimulation; and a stimulation presentation controller configured to control the stimulation presented by the stimulation presenting unit, wherein the stimulation presentation controller includes: a setting means configured to set a resting task and a stimulating task to be presented to the examinee; a detecting means configured to detect a response of the examinee to the resting task and the stimulating task; and a task presentation control means configured to determine whether or not a sufficient degree of stability exists for a parameter, on the basis of the detected response when the resting task is presented, and configured to control the presentation of the resting task or the stimulating task on the basis of the determination of whether or not a sufficient degree of stability exists for a parameter, wherein said degree of stability is of at least one parameter selected from: utterance reaction time, utterance frequency, right answer rate, reaction time average value, reaction time standard deviation, and reaction frequency.