A technique for controlling power for V2X communication is provided. The apparatus includes a reception message analysis process configured to analyze headers of reception messages received from communication apparatuses of roadside apparatuses and surrounding vehicles located around a vehicle, a message loss checking process configured to check whether or not loss of the reception messages occurs by counting sequential numbers included in the headers of the reception messages, a density analysis process configured to analyze a density for each of communication apparatuses located in a communication radius of preset transmission power from the vehicle when the message loss checking process determines that the loss of the reception messages occurs, and a transmission power determination process configured to determine transmission power for V2X communication by deducting the preset transmission power in units of reference power according to the density when the density around the vehicle exceeds a reference value.