A portable electronic device comprising: a flexible display unit having a front surface and a rear surface; and a folding unit in contact with the rear surface of the flexible display unit, the folding unit including a plurality of blocks and a connection unit, the connection unit connecting the plurality of blocks to each other, wherein at least one or more of the plurality of blocks are configured to move along a curved path when the flexible display unit transitions to and from a first state and a second state, wherein the flexible display unit is flat in the first state and folded in the second state, wherein the connection unit comprises a plurality of links attached to the ends of the plurality of blocks and wherein each of the plurality of links connects the ends of two neighboring blocks such that the blocks are movable relative to each other, characterized in that the plurality of links comprise a first group of links sequentially connected to each other, and a second group of links sequentially connected to each other, wherein each of the links of the first and second groups of links (265a, 265b) connects a front, side portion of one block to a rear, side portion of a neighboring block, and wherein each of the links of the first group crisscross a corresponding one of the links of the second group, wherein the connection unit further comprises first connections shafts (263 a) for connecting at least part of the links to the one side, and second connecting shafts for connecting at least part of the links to the other side, wherein the plurality of blocks comprises first connection grooves connected to the first connection shaft, respectively at the one side, and second connection grooves connected to the second connection shaft respectively at the other side, wherein the first connection groove is configured as a slit long formed in one direction, such that first connection shaft is moveable in the first connection groove. a flexible display unit having a front surface and a rear surface; and a folding unit in contact with the rear surface of the flexible display unit, the folding unit including a plurality of blocks and a connection unit, the connection unit connecting the plurality of blocks to each other, wherein at least one or more of the plurality of blocks are configured to move along a curved path when the flexible display unit transitions to and from a first state and a second state, wherein the flexible display unit is flat in the first state and folded in the second state, wherein the connection unit comprises a plurality of links attached to the ends of the plurality of blocks and wherein each of the plurality of links connects the ends of two neighboring blocks such that the blocks are movable relative to each other, characterized in that the plurality of links comprise a first group of links sequentially connected to each other, and a second group of links sequentially connected to each other, wherein each of the links of the first and second groups of links (265a, 265b) connects a front, side portion of one block to a rear, side portion of a neighboring block, and wherein each of the links of the first group crisscross a corresponding one of the links of the second group, wherein the connection unit further comprises first connections shafts (263 a) for connecting at least part of the links to the one side, and second connecting shafts for connecting at least part of the links to the other side, wherein the plurality of blocks comprises first connection grooves connected to the first connection shaft, respectively at the one side, and second connection grooves connected to the second connection shaft respectively at the other side, wherein the first connection groove is configured as a slit long formed in one direction, such that first connection shaft is moveable in the first connection groove.