An apparatus for analyzing an active material of a secondary battery may include: a first electrode; a piezoelectric layer on the first electrode; a second electrode on the piezoelectric layer, configured to provide a voltage having a polarity opposite to a polarity of the first electrode; and/or an insulating layer on the second electrode and including a through hole exposing a portion of the second electrode. A method of analyzing an active material of a secondary battery may include: disposing an active material in a through hole of a bulk acoustic resonator, in which a first electrode, a piezoelectric layer, a second electrode, and an insulating layer are stacked; measuring a resonance frequency of the resonator by applying an electric signal to the first and second electrodes of the resonator; and/or measuring a weight of the active material in the through hole, based on the measured resonance frequency.