A gait disorder support apparatus, comprising: - a power unit to be mounted around a knee joint of either a right leg or a left leg of a wearer; - a lower back unit to be mounted at a lower back of the wearer; and - a pair of shoes (4A, 4B) to be worn by both feet of the wearer, wherein: - the power unit includes an actuator and a drive unit that is configured to drive frames (12, 14) to be mounted on a thigh part and a lower leg part relatively around a rotation axis corresponding to the knee joint of the wearer; - each of the pair of shoes (4A, 4B) is configured to hold a wearer's foot from toes to an ankle, includes a floor reaction force sensor at a shoe sole, and is capable of measuring a load by using the sensor; - the power unit includes: - a gait cycle calculation unit (20, 21, 80) that is configured to calculate, as a gait cycle of the wearer, an occurrence timing regarding the leg on which the drive unit is mounted among occurrence timings of a peak value of the measured load; - an onset sign detection unit (20, 21, 80) that is configured to detect a sign indicating a possible onset of a gait disorder associated with a motor symptom of the wearer on a basis of a correlation between the gait cycle calculated by the gait cycle calculation unit (20, 21, 80) and a reduction ratio of the gait cycle as compared to a gait cycle calculated immediately before the above-mentioned calculation; and - a control unit (20, 21, 80) that is configured to control the drive unit so that the drive unit applies assist power to the knee joint of the wearer when the sign indicating the possible onset of the gait disorder is detected by the onset sign detection unit (20, 21, 80), while controlling the drive unit so that driving torque by the drive unit does not interfere with a gait motion of the wearer when the sign indicating the possible onset of the gait disorder is not detected, wherein: - the control unit (20, 21, 80) is configured to generate the assist power in synchronization with timing when a gravity center position of the wearer is located at the wearer's leg on which the drive unit is not mounted. - a power unit to be mounted around a knee joint of either a right leg or a left leg of a wearer; - a lower back unit to be mounted at a lower back of the wearer; and - a pair of shoes (4A, 4B) to be worn by both feet of the wearer, - the power unit includes an actuator and a drive unit that is configured to drive frames (12, 14) to be mounted on a thigh part and a lower leg part relatively around a rotation axis corresponding to the knee joint of the wearer; - each of the pair of shoes (4A, 4B) is configured to hold a wearer's foot from toes to an ankle, includes a floor reaction force sensor at a shoe sole, and is capable of measuring a load by using the sensor; - the power unit includes: - a gait cycle calculation unit (20, 21, 80) that is configured to calculate, as a gait cycle of the wearer, an occurrence timing regarding the leg on which the drive unit is mounted among occurrence timings of a peak value of the measured load; - an onset sign detection unit (20, 21, 80) that is configured to detect a sign indicating a possible onset of a gait disorder associated with a motor symptom of the wearer on a basis of a correlation between the gait cycle calculated by the gait cycle calculation unit (20, 21, 80) and a reduction ratio of the gait cycle as compared to a gait cycle calculated immediately before the above-mentioned calculation; and - a control unit (20, 21, 80) that is configured to control the drive unit so that the drive unit applies assist power to the knee joint of the wearer when the sign indicating the possible onset of the gait disorder is detected by the onset sign detection unit (20, 21, 80), while controlling the drive unit so that driving torque by the drive unit does not interfere with a gait motion of the wearer when the sign indicating the possible onset of the gait disorder is not detected, wherein: - a gait cycle calculation unit (20, 21, 80) that is configured to calculate, as a gait cycle of the wearer, an occurrence timing regarding the leg on which the drive unit is mounted among occurrence timings of a peak value of the measured load; - an onset sign detection unit (20, 21, 80) that is configured to detect a sign indicating a possible onset of a gait disorder associated with a motor symptom of the wearer on a basis of a correlation between the gait cycle calculated by the gait cycle calculation unit (20, 21, 80) and a reduction ratio of the gait cycle as compared to a gait cycle calculated immediately before the above-mentioned calculation; and - a control unit (20, 21, 80) that is configured to control the drive unit so that the drive unit applies assist power to the knee joint of the wearer when the sign indicating the possible onset of the gait disorder is detected by the onset sign detection unit (20, 21, 80), while controlling the drive unit so that driving torque by the drive unit does not interfere with a gait motion of the wearer when the sign indicating the possible onset of the gait disorder is not detected, wherein: - the control unit (20, 21, 80) is configured to generate the assist power in synchronization with timing when a gravity center position of the wearer is located at the wearer's leg on which the drive unit is not mounted.