A separation membrane structure comprising a porous support, a first glass seal, and a separation membrane. The porous support includes through-holes which connect a first end surface and a second end surface. The first glass seal is configured to cover the first end surface. The separation membrane is formed on an inner surface of the through-holes. The first glass seal has a first seal body part and a first extension part. The first seal body part is disposed on the first end surface. The first extension part is connected to the first seal body part and disposed on the inner surface of the through-holes. The separation membrane has a first connection part connected to the first extension part of the first glass seal. A first thickness of the first connection part is less than or equal to 10 microns, and less than or equal to 3.2 times a center thickness at a longitudinal center of the separation membrane.