This paper investigates the Fourier transform of a hidden variable fractal interpolation function with function scaling factors, which generalizes the Fourier transform of hidden variable fractal interpolation function with constant scaling factors. Furthermore, the Fourier transform of quadratic hidden variable fractal interpolation function with function scaling factors is also investigated. With an aim of maximizing the flexibility of hidden variable fractal interpolation function and quadratic hidden variable fractal interpolation function, a class of iterated function systems involving function scalings is chosen for the present study. © 2023, Chulalongkorn University, Faculty of Fine and Applied Arts. All rights reserved.