A roller support mechanism includes a pair of support plates, concave groove portions, and sliding bearing portions. The support plates are formed from an elastic material and disposed to face each other. The concave groove portions are formed in the support plates and each include an opening portion, two arc rims, and a straight line rim. The arc rims extend in a groove depth direction of the concave groove portion from opposite ends of the opening portion. The straight line rim extends straightly and connects extention ends of the arc rims. The sliding bearing portions have bearing holes in which a rotation shaft of a roller member is inserted. In a state where the rotation shaft is inserted in the bearing holes, the sliding bearing portions are pressed into the concave groove portions so as to be in close contact with their inner circumferential surfaces and unrotatably attached to them.