The present invention relates to a brush seal device for shutting off a gap between splitting surfaces so as to prevent sealed fluid from leaking out from the gap. Each of the splitting surfaces is composed of splitting direction-extending surfaces that extend in such a direction as to split split-body parts and a longitudinal surface that extends in the longitudinal direction of the split-body parts and that forms a step-like surface interposed between the splitting direction-extending surfaces. Shutoff means for sealing the gap between the splitting direction-extending surfaces so as to prevent leakage of sealed fluid is provided in the gap between the splitting direction-extending surfaces that are combined with each other.