A thigh exercise device includes a curved track, two foot pedal assemblies movably attached to the curved track and respectively having a guide pulley, and two resistance assemblies each having two pulleys rotatably mounted on the curved track and a resistance band wound around the pulleys and the guide pulley of one of the foot pedal assemblies. When the foot pedal assemblies are moved along the curved track, the resistance bands can be pulled tight by the guide members of the foot pedal assemblies such that a user can strengthen thigh muscles through the tension provided by the resistance bands.