According to an embodiment, a flow passage structure includes a member. The member has a surface and is provided with a first passage, a plurality of first openings, a second passage, and a plurality of second openings. The first passage includes a plurality of first closed path portions connected to each other. The first openings is connected to the first passage and is opened in the surface. The second passage includes a plurality of second closed path portions connected to each other. The second openings is connected to the second passage and is opened in the surface. The first closed path portions pass through the second closed path portions while being isolated from the second closed path portions. The second closed path portions pass through the first closed path portions while being isolated from the first closed path portions.