A real-time clock frequency correction device includes: a quartz oscillator outputting an oscillating signal including a plurality of oscillating pulses with a frequency; a control unit setting a first integer, a second integer, a first number corresponding to the first integer, and a second number corresponding to the second integer according to the frequency, wherein the first integer is a minimum integer that is larger than the frequency, and the second integer is a maximum integer that is smaller than the frequency; a multiplexer outputting the first integer for the first number of times and the second integer for the second number times; and a counter, coupled to the multiplexer and the quartz oscillator, for counting the number of oscillating pulses according to one of the first integer and the second integer and thereby outputting a pulse.