The frequency response of pinned vortex lattice in type-II superconductors is investigated. If frequency is not too low than the AC-absorption is caused by oscillations of the vortex lattice near equilibrium state (Campbell regime). We calculate the field and temperature dependencies of both Campbell penetration depth and surface resistance, taking into account the effect of the thermal depinning. In the region of low frequencies jumps of lattice regions between different metastable states (two-level systems) come into play and give main contribution to the AC-response. The field and temperature dependencies of the penetration depth and surface resistance in the last region are also found.