An example wireless power transmitter may include a transmission coil, a converter configured to output a driving voltage, an inverter configured to output AC power to the transmission coil using the driving voltage, and a controller. The controller may be configured to identify a first voltage at one point within the wireless power transmitter while power is wirelessly transmitted through the transmission coil. The controller may be configured to perform at least one operation for providing a first packet for reduction in modulation depth of a wireless power receiver to the wireless power receiver based on a peak-to-peak value identified to be larger than a first reference value according to the first voltage.