The present invention aims to provide a modified polytetrafluoroethylene fine powder capable of providing a stretched body having high strength, a small pore size, and excellent homogeneity. The modified polytetrafluoroethylene fine powder of the present invention has non-melt-processability, has a standard specific gravity of 2.155 or lower, includes 0.015 mol % or more of a polymer unit derived from perfluoro(methyl vinyl ether) in all the monomer units, is obtained by emulsion polymerizing tetrafluoroethylene and at least the perfluoro(methyl vinyl ether) in the presence of a fluorosurfactant having a LogPOW value of 3.4 or lower, and has an extrusion pressure of 20.0 MPa or lower.