A Fractional-order Proportional-Integrated-Derivative (FO-PID) controller is designed for the Buck converter, which in the control parameters are optimized by Antlion Optimization (ALO) algorithm. The Fractional-Order concept is a beneficial scheme that can provide several advantages such as lower sensitivity to parametric variation and noise. Also, the ALO algorithm is a modern nature-inspired algorithm used to tune the PID gains with better results under-constrained problems with diverse search spaces. Considering numerous disturbance on power converters, a FO-PID controller can be an appropriate alternative since it has a good robustness against harmful disturbances and has simple structure to be implemented in industrial applications. To better examine the superiority of the proposed method, conventional FO-PID and PID control techniques are also designed to be compared with this work. Both simulation and experimental results verify the robustness of the proposed method in different challenging scenarios.