A mode-locked Er:fiber laser-based optical frequency comb with high stability in the repetition frequency and carrier-envelope offset (CEO) frequency is realized. The CEO beat signal was detected right after the supercontinuum generation by a compact single-beam f-2f self-referencing interferometer, which does not require further delay compensation. The stabilized repetition frequency has an out-of-loop tracking stability of 1.3×10-13/ √τ for an integration time τ less than 1000 s, which is limited by the stability of the frequency measurement system. The stabilized CEO frequency has a residual fluctuation of 0.52 mHz measured with a 1 s gate time. This is, to our knowledge, the highest tracking stability realized for fiber laser-based optical frequency comb.