The present invention relates to a brush seal device (1) 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 (3D) that extend in such a direction as to split split-body parts (2) and a longitudinal surface (3L) that extends in the longitudinal direction of the split-body parts (2) and that forms a step-like surface interposed between the splitting direction-extending surfaces (3D). Shutoff means (10) for sealing the gap between the splitting direction-extending surfaces (3D) so as to prevent leakage of sealed fluid is provided in the gap between the splitting direction-extending surfaces (3D) that are combined with each other.