An aircraft seat structure comprising: a first seat unit having a first seat region in which passengers are able to sit, and a first side region adjacent in a direction perpendicular to a longitudinal direction of the first seat region; and a second seat unit having a second seat region in which passengers are able to sit, and a second side region adjacent in a direction perpendicular to a longitudinal direction of the second seat region; wherein: the first side region is provided on one side of the first seat region along a direction that intersects a traveling direction of an aircraft, and the second side region is provided on another side of the second seat region along the direction that intersects the traveling direction of the aircraft, the first side region and the second seat region are joined in a state in which a portion of the second seat region is inserted into the first side region, the first side region and the second side region are separated by a partition wall (114, 124), the partition wall (114, 124) has an inclined surface tilted toward the second seat unit; a locking device being attached to the partition wall (114, 124), the locking device including a locking portion, characterized in that a monitor (117, 127) is tiltably mounted to the inclined surface, a seat of the second seat region can be changed in form between an upright state and a reclining state and the monitor (117, 127) can be displaced between a tilted position corresponding to the upright state and a tilted position corresponding to the reclining state; when the seat of the second seat region is in the upright state, the locking portion of the locking device of the seat of the second seat region is configured to abut a back surface of the monitor (117, 127); and the locking portion of the locking device of the seat of the second seat region is configured to abut a front surface of the monitor (117, 127) when the seat of the second seat region is in the reclining state. a first seat unit having a first seat region in which passengers are able to sit, and a first side region adjacent in a direction perpendicular to a longitudinal direction of the first seat region; and a second seat unit having a second seat region in which passengers are able to sit, and a second side region adjacent in a direction perpendicular to a longitudinal direction of the second seat region; wherein: the first side region is provided on one side of the first seat region along a direction that intersects a traveling direction of an aircraft, and the second side region is provided on another side of the second seat region along the direction that intersects the traveling direction of the aircraft, the first side region and the second seat region are joined in a state in which a portion of the second seat region is inserted into the first side region, the first side region and the second side region are separated by a partition wall (114, 124), the partition wall (114, 124) has an inclined surface tilted toward the second seat unit; a locking device being attached to the partition wall (114, 124), the locking device including a locking portion, characterized in that a monitor (117, 127) is tiltably mounted to the inclined surface, a seat of the second seat region can be changed in form between an upright state and a reclining state and the monitor (117, 127) can be displaced between a tilted position corresponding to the upright state and a tilted position corresponding to the reclining state; when the seat of the second seat region is in the upright state, the locking portion of the locking device of the seat of the second seat region is configured to abut a back surface of the monitor (117, 127); and the locking portion of the locking device of the seat of the second seat region is configured to abut a front surface of the monitor (117, 127) when the seat of the second seat region is in the reclining state. the first side region is provided on one side of the first seat region along a direction that intersects a traveling direction of an aircraft, and the second side region is provided on another side of the second seat region along the direction that intersects the traveling direction of the aircraft, the first side region and the second seat region are joined in a state in which a portion of the second seat region is inserted into the first side region, the first side region and the second side region are separated by a partition wall (114, 124), the partition wall (114, 124) has an inclined surface tilted toward the second seat unit; a locking device being attached to the partition wall (114, 124), the locking device including a locking portion, characterized in that a monitor (117, 127) is tiltably mounted to the inclined surface, a seat of the second seat region can be changed in form between an upright state and a reclining state and the monitor (117, 127) can be displaced between a tilted position corresponding to the upright state and a tilted position corresponding to the reclining state; when the seat of the second seat region is in the upright state, the locking portion of the locking device of the seat of the second seat region is configured to abut a back surface of the monitor (117, 127); and the locking portion of the locking device of the seat of the second seat region is configured to abut a front surface of the monitor (117, 127) when the seat of the second seat region is in the reclining state.