The present invention discloses an airtight test apparatus and an airtight test method using the same for testing an airtight property of a case assembled with a plurality of additional members thereon in which the case has through holes corresponding to the additional members. The airtight test apparatus comprises a base, a top plate and a plurality of sealing members selectively and detachably disposed on the top plate. The top plate is capable of moving towards the base to allow the sealing members to correspondingly seal the through holes. During test, the case is placed on the base to form a gas chamber, an air-extracting is performed for the gas chamber and an air pressure is detected. When the detected air pressure is larger than a predetermined value, the sealing members can be selectively utilized to seal the corresponding through holes for determining which through holes have poor airtight property.