Provided is an apparatus for calibrating a transmission path, the apparatus including one or more couplers to separate, by one or more paths, one or more input signals input from an input terminal of one or more antennas, a power detector to detect amplitude of one or more path signals separated by the one or more paths, a power distributor to distribute any one of the one or more path signals, one or more mixers to mix a distribution signal distributed by the power distributor with the one or more path signals, a low-pass filter to remove a high-frequency component of a mixed signal mixed by the one or more mixers; and a voltage detector to detect amplitude of one or more filter pass signals with the high-frequency component removed.