A door device with pressure difference mitigating mechanism, comprising: a door frame; a door divided into two parts to left and right, that is, a hanging door and a door-end door pivotally supported by the hanging door; wherein one side of the hanging door defines a notched opening while portions constituting upper and lower bearing portions (24a, 24b) are left, a stepped contracted portion of the door-end door being fitted in this notched opening and pivotally supported by the bearing portions (24a, 24b), a rotating shaft of the door-end door pivotally supported by the hanging door being not made eccentric but set at a substantially centre position of the door-end door; a handle for opening/closing the door, a latch A of the door-end door to the door frame, and a latch B of the door-end door to the hanging door; and characterised in that: the latch B is a roller catch latch or a magnet catch type latch; the relationship PA H > PB H + LB H is satisfied so that only the door-end door is opened when the pressure difference is generated; where: a force required against a releasing force of the latch B (handle position): LB H a load acting on the entire door by an air pressure difference (acting in a closing direction) (handle position): PA H a load acting on the door-end door by the air pressure difference (acting in the closing direction) (handle position), PB H a door frame; a door divided into two parts to left and right, that is, a hanging door and a door-end door pivotally supported by the hanging door; wherein one side of the hanging door defines a notched opening while portions constituting upper and lower bearing portions (24a, 24b) are left, a stepped contracted portion of the door-end door being fitted in this notched opening and pivotally supported by the bearing portions (24a, 24b), a rotating shaft of the door-end door pivotally supported by the hanging door being not made eccentric but set at a substantially centre position of the door-end door; a handle for opening/closing the door, a latch A of the door-end door to the door frame, and a latch B of the door-end door to the hanging door; and characterised in that: the latch B is a roller catch latch or a magnet catch type latch; the relationship PA H > PB H + LB H is satisfied so that only the door-end door is opened when the pressure difference is generated; where: a force required against a releasing force of the latch B (handle position): LB H a load acting on the entire door by an air pressure difference (acting in a closing direction) (handle position): PA H a load acting on the door-end door by the air pressure difference (acting in the closing direction) (handle position), PB H the latch B is a roller catch latch or a magnet catch type latch; the relationship PA H > PB H + LB H is satisfied so that only the door-end door is opened when the pressure difference is generated; where: a force required against a releasing force of the latch B (handle position): LB H a load acting on the entire door by an air pressure difference (acting in a closing direction) (handle position): PA H a load acting on the door-end door by the air pressure difference (acting in the closing direction) (handle position), PB H a force required against a releasing force of the latch B (handle position): LB H a load acting on the entire door by an air pressure difference (acting in a closing direction) (handle position): PA H a load acting on the door-end door by the air pressure difference (acting in the closing direction) (handle position), PB H