The invention aims to provide a nanofiber having self-heating properties and biologically active substance release properties, which can release a drug at the same time as self-heating, and can be safely used on a human body without diffusing self-heating nanoparticles, a production method for the same, and a nonwoven fabric having self-heating properties and biologically active substance release capabilities. A fiber is provided having a diameter in a range of 50 nm to 50 μm, and a length of 100 times the diameter or more, the fiber including: self-heating particles that generate heat in response to stimulation from outside; a stimulation-responsive polymer of which physical properties change by directly or indirectly reacting due to the stimulation; and a biologically active substance that is held by the stimulation-responsive polymer, in which the biologically active substance is released to the outside in response to the changes in the physical properties of the stimulation-responsive polymer, a production method for the same, and a nonwoven fabric having self-heating properties and biologically active substance release capabilities.