An optical fiber preform includes a silica-glass core portion, and a cladding portion surrounding the core portion, the cladding portion being composed of a fluorine-containing silica glass having a lower refractive index than the core portion, the core portion including a first region that does not include the central axis thereof, the first region containing a first dopant selected from sodium, potassium, and compounds thereof, and a second region that includes the central axis, the second region containing a second dopant that reduces the viscosity of the silica glass, the second dopant having a diffusion coefficient of 1×10−12 cm2/s or more and less than the first dopant at 2,000° C. to 2,300° C., in which the entire core portion has an average first dopant concentration of 10 atomic ppm or more and 2,000 atomic ppm or less and an average second dopant concentration of 10 atomic ppm or more.