The present invention provides a variable-focus lens capable of freely changing the refractive power and operating with a reduced deterioration in performance and an image taking apparatus having a focal-length-variable image taking lens including the variable-focus lens. The variable-focus lens includes: a lens body having an electromagnetic field generator which changes the focal length of the light passage region by moving, by an electromagnetic force, light-transmissive nanoparticles which are dispersed in a light-transmissive dispersion medium enclosed in a container having the shape of a lens, and which have a refractive index different from the refractive index of the dispersion medium; a moving mechanism which moves the lens body in an optical axis direction; and a focal length adjustment section which changes the focal length of the lens body by controlling an electromagnetic field generated by the electromagnetic field generator.