A cap removal apparatus for a vacuum blood collection tube is configured to remove a cap from the collection tube of which an opening is closed by the cap so that the tube is kept under vacuum inside. The cap removal apparatus comprises, a tube clamping mechanism which clamps the collection tube upright in a cap removal position, a chuck mechanism which is disposed in the cap removal position and chucks the cap of the collection tube, seal pressure reduction unit which is disposed in the a chuck mechanism and configured to seal a region around the opening including the cap and reduce the pressure of the sealed region to substantially the same level as the internal pressure of the collection tube when the cap is chucked, and a lift mechanism which raises the chuck mechanism from a cap chucking position, thereby removing the cap from the collection tube.