To provide a fiber or fiber product containing a dyed nanofiber aggregate having coloring property in a level which is practically free from trouble, in the dyed nanofiber aggregate.

In the dyed nanofiber aggregate, a water-insoluble dye is carried in spaces of single fibers of a nanofiber aggregate having 10-200 nm single fiber diameter (average) and ≤3% ratio of area having ≥200 nm single fiber diameter and having a slight dispersion in fiber diameter.