A sample feeding apparatus includes a first cylinder, a second cylinder, and a sealing section. The first cylinder is configured to be mounted with a sample tube. The second cylinder is configured to move the first cylinder between a first position and a second position, the first position being for mounting of the sample tube, the second position being for feeding of a sample in the sample tube. The sealing section is configured to cover the sample tube, the sample tube being mounted to the first cylinder being at the second position, the first cylinder applying pressure to an inner space of the sealing section at the second position.