CVT controller has rotation speed sensors detecting driving and driven wheel rotation speed; driving and driven wheel speed difference detection unit detecting wheel speed difference Δvfr; and bad road judgment unit judging that road is bad road when Δvfr is first value Δvfr_br or greater. CVT controller further has first belt clamping force increase unit increasing belt clamping force in case where road is judged to be bad road, as compared with case where road is not judged to be bad road; vibration detection unit detecting vehicle speed vibration fvsp; and second belt clamping force increase unit increasing belt clamping force when Δvfr is second value Δvfr_psec or greater or when fvsp is third value fvsp_psec or greater in case where road is not judged to be bad road, as compared with case where Δvfr is less than Δvfr_psec and case where fvsp is less than fvsp_psec.