The present invention relates to a filter and, more particularly, to a tuning circuit of a filter for correcting a cut-off frequency of the filter. The tuning circuit comprises a current generation unit having a first transistor and a variable resistor unit, and a capacitance correction unit having a second transistor, a capacitor unit, an up-down counter and a selection unit for selecting a control path of the up-down counter for varying the resistance or capacitance.