Provided are a focus control device that makes it possible to enhance the precision of phase difference calculation, a lens device, an imaging device, a focus control method, and a program. A digital camera is provided with: a phase difference calculation unit 11a that calculates the phase difference between a signal group output from a plurality of phase difference detection pixels 52A and a signal group output from a plurality of phase difference detection pixels 52B; a lens drive control unit 11c that drives a focus lens in accordance with a drive amount corresponding to the phase difference; a coefficient a(n) for converting the phase difference calculated at a time t(n) into a drive amount; and a phase difference prediction unit 11b that calculates a prediction value for the phase difference at a time t(n+1) on the basis of the difference delta m(n+1) between the drive amount and the movement amount of the focus lens from the time t(n) at a time t(n+1) after movement of the focus lens in accordance with the drive amount has been initiated. The phase difference calculation unit 11a calculates the phase difference on the basis of the prediction value and the results of correlation calculation.