In this invention, to provide a compact zoom lens having a small number of optical element groups to be driven and a simple moving mechanism, at least one of a plurality of optical element groups arranged in the lens system includes a refractive power variable element of a transmission type which has a compensation function to correct focus movement caused by zooming and a focus function to correct focus movement caused by a variation in inter-object distance. The refractive power variable element is a liquid optical element including a first liquid having a conductivity or a polarity and a second liquid which is not mixed with the first liquid, the first liquid and the second liquid being enclosed in a container fluid-tight so as to define an interface therebetween having a predetermined shape, the liquid optical element being arranged such that a refractive power thereof is adjusted by changing a curvature of the interface.