Labyrinth seal and gas turbine

A labyrinth seal comprising:

• a first structure including at least three seal fins located at intervals in an axial direction;
• and
• a second structure opposed to the first structure and including at least three step surfaces whose radial positions are different from each other, a radial gap being between each seal fin and a corresponding closest step surface, wherein:
• the second structure is such that when any one of the seal fins is regarded as a reference seal fin, a portion of the second structure which is located downstream of the reference seal fin does not overlap the reference seal fin when viewed in the axial direction;
• the second structure includes an inlet wall located upstream of a most upstream one of the seal fins, a radial gap being between the inlet wall and the first structure;
• and
• an axial position of each seal fin coincides with a downstream end portion of the corresponding closest step surface.