A portable information device includes: a first chassis; a second chassis coupled to be rotatable relative to the first chassis; a first plate fixed to the first chassis; a second plate fixed to the second chassis to be adjacent to the first plate; a display having a bending region; a first locking piece protruding from the first plate beyond a first end face to be able to come into contact with and separate from the second plate; a second locking piece protruding from the second plate beyond a second end face to be able to come into contact with and separate from the first plate; and a protruding part provided to protrude from at least one of the first end face and the second end face toward the other to come into contact with the other in a flat plate form.