A balance training device includes at least one supporting base and at least one plank member. The supporting base includes a plank connecting portion formed with a plank coupling groove that opens upwardly. The plank coupling groove includes a first groove section and a second groove section that intersects the first groove section. The plank member includes a plate portion and a rib structure disposed on a bottom face of the plate portion. The rib structure removably engages the plank coupling groove of the supporting base. The rib structure includes a first rib part to engage the first groove section and a second rib part to engage the second groove section.