A varifocal lens capable of exhibiting high lens performance even with low lens power, and also capable of realizing a comparatively large aperture includes a first elastic membrane arranged between a first medium and a second medium. The first elastic membrane is capable of elastic deformation by pressure from the first medium or the second medium. A drive section causes change in curvature of the first elastic membrane by causing variation in pressure or volume of the first medium or the second medium. The first tensile force applying section applies isotropic tensile force to the first elastic membrane.