A holding device disposed in a bio-detecting instrument for holding a test strip is provided, wherein the holding device comprises a first casing, a second casing, an ejecting member, and an elastic member. The second casing is assembled with the first casing to form an accommodating space, wherein the sensing terminals are extended into the accommodating space. The ejecting member comprises a push rod configured to be reciprocated in the accommodating space. The elastic member is configured to be compressed by driving the ejecting member to an ejecting position, where the push rod enters the accommodating space and is adapted to push the test strip outward without being contact with the sensing terminals, and the elastic member is configured to be released by drawing the push rod back from the accommodating space to an initial position.