A molded body treating apparatus includes a support, at least one flat plate and a first movement mechanism. The support is configured to support a honeycomb molded body which has a first end portion and a second end portion in a longitudinal direction of the honeycomb molded body and which includes a plurality of cells each extending along the longitudinal direction from a first end at the first end portion to a second end at the second end portion. Either the first end or the second end of each of the plurality of cells is sealed with a plug material paste. The first movement mechanism is configured to move the at least one flat plate along the longitudinal direction to press the either one of the first and second end portions.