To reduce the possibility of contamination in case of switching a pre-filter in a safety cabinet having a pre-filter and an HEPA filter.

In a safety cabinet 1, a front shutter 4 is arranged at the front side of a workspace 3 installed in a body case 1a, and a pre-filter 11 is arranged at the back wall side, and an HEPA filter 12 and an intake/exhaust unit 5 are installed at the back side of the pre-filter, wherein air sucked from a workspace opening 6 formed at the lower part of the front shutter to the workspace by the intake/exhaust unit is filtered out by the pre-filter and the HEPA filter in this order, and exhausted outside of the body case, and the pre-filter is arranged with its filter face set in a vertical direction at the lower part of the back wall part of the workspace, and a holding structure 16 by which the pre-filter is held so as to be detached and an outlet are installed in at least either the workspace or the body case.