A low-pressure process apparatus for processing a substrate comprises a base, a stage, a housing and at least one first roller set. The stage is disposed on the base for supporting the substrate. The housing is detachably disposed on the base moving between a first position and a second position, wherein when the housing is in a first position, the housing and the base form a chamber to receive the stage. When the housing is detached, the first roller set contacts and supports the housing to facilitate movement thereof in a first horizontal direction.