A cordless hair straightener, comprising: a body which includes a battery including an input and an output and charged by an external power supply through the input; a first heater unit and a second heater unit electrically connected to the output of the battery; a first housing accommodating at least a part of the body and at least a part of the first heater unit, and moving the first heater unit between a closed position and an open position; and a second housing accommodating at least a part of the body and at least a part of the second heater unit, and moving the second heater unit between a closed position and an open position; wherein the first housing is engaged with a first hinge disposed in a lower portion of the body and is movable on the first hinge between the closed position and the open position, characterized in that the second housing is engaged with a second hinge which is different from the first hinge and disposed in the lower portion of the body, and is movable on the second hinge between the closed position and the open position; the first hinge includes a first protrusion having a first inclined surface and a second protrusion having a second inclined surface, the first protrusion and the second protrusion are disposed in opposite directions (B, C) on the same axis, and when external force is applied to the first inclined surface and the second inclined surface in a predetermined direction, the first protrusion is moved in the first direction, and the second protrusion is moved in the second direction opposite to the first direction, allowing the first housing to be attached and detached. a body which includes a battery including an input and an output and charged by an external power supply through the input; a first heater unit and a second heater unit electrically connected to the output of the battery; a first housing accommodating at least a part of the body and at least a part of the first heater unit, and moving the first heater unit between a closed position and an open position; and a second housing accommodating at least a part of the body and at least a part of the second heater unit, and moving the second heater unit between a closed position and an open position; wherein the first housing is engaged with a first hinge disposed in a lower portion of the body and is movable on the first hinge between the closed position and the open position, characterized in that the second housing is engaged with a second hinge which is different from the first hinge and disposed in the lower portion of the body, and is movable on the second hinge between the closed position and the open position; the first hinge includes a first protrusion having a first inclined surface and a second protrusion having a second inclined surface, the first protrusion and the second protrusion are disposed in opposite directions (B, C) on the same axis, and when external force is applied to the first inclined surface and the second inclined surface in a predetermined direction, the first protrusion is moved in the first direction, and the second protrusion is moved in the second direction opposite to the first direction, allowing the first housing to be attached and detached.