Disclosed herein are a soil moisture sensor and an operating method thereof. The soil moisture sensor includes a first probe including a pair of first electrodes extending in a first direction; a first resonance circuit connected to the pair of first electrodes of the first probe through a pair of first ports, and configured such that a first AC signal is applied thereto; a second resonance circuit having the same impedance as the first resonance circuit, and configured such that a second AC signal having the same characteristics as the first AC signal while being a reference AC signal is applied thereto; and a determination circuit configured to receive a first electrical signal and a second electrical signal and to determine the moisture in the soil based on the first resonant frequency of the first electrical signal and the second resonant frequency of the second electrical signal.