A washing machine, comprising: an outer tank in which washing water can be held; an inner tank which is installed rotatably inside the outer tank; and an auxiliary washing unit which is installed inside the inner tank and is configured to rotate integrally with the inner tank, the washing machine characterized in that: the auxiliary washing unit has a first water channel formed therein that is configured so that laundry in the inner tank receives an impact from the washing water which, after flowing into the first water channel from a first side of the outer tank, flows out of the first water channel to the inside of the inner tank by a rotational force generated when the inner tank is rotated in a forward direction, and a second water channel formed therein that is configured so that laundry in the inner tank receives an impact from the washing water which, after flowing into the second water channel from a second side of the outer tank, flows out of the second water channel to the inside of the inner tank by a rotational force generated when the inner tank is rotated in a reverse direction, wherein the auxiliary washing unit comprises a supporting member in which the first water channel and the second water channel are formed; and a projection member which is coupled to and supported by the supporting member and that lifts the laundry by trapping while the inner tank is rotated, and wherein an inlet of each of the first water channel and the second water channel is formed in the supporting member and the inlet is opened in a tangential direction of the inner tank, so that the washing water flowing in from the side of the outer tank flows out to the inside of the inner tank due to the rotational force being generated when the inner tank is rotated, thereby impacting the laundry which is trapped on the projection member. an outer tank in which washing water can be held; an inner tank which is installed rotatably inside the outer tank; and an auxiliary washing unit which is installed inside the inner tank and is configured to rotate integrally with the inner tank, the washing machine characterized in that: the auxiliary washing unit has a first water channel formed therein that is configured so that laundry in the inner tank receives an impact from the washing water which, after flowing into the first water channel from a first side of the outer tank, flows out of the first water channel to the inside of the inner tank by a rotational force generated when the inner tank is rotated in a forward direction, and a second water channel formed therein that is configured so that laundry in the inner tank receives an impact from the washing water which, after flowing into the second water channel from a second side of the outer tank, flows out of the second water channel to the inside of the inner tank by a rotational force generated when the inner tank is rotated in a reverse direction, wherein the auxiliary washing unit comprises a supporting member in which the first water channel and the second water channel are formed; and a projection member which is coupled to and supported by the supporting member and that lifts the laundry by trapping while the inner tank is rotated, and the auxiliary washing unit has a first water channel formed therein that is configured so that laundry in the inner tank receives an impact from the washing water which, after flowing into the first water channel from a first side of the outer tank, flows out of the first water channel to the inside of the inner tank by a rotational force generated when the inner tank is rotated in a forward direction, and a second water channel formed therein that is configured so that laundry in the inner tank receives an impact from the washing water which, after flowing into the second water channel from a second side of the outer tank, flows out of the second water channel to the inside of the inner tank by a rotational force generated when the inner tank is rotated in a reverse direction, wherein the auxiliary washing unit comprises a supporting member in which the first water channel and the second water channel are formed; and a projection member which is coupled to and supported by the supporting member and that lifts the laundry by trapping while the inner tank is rotated, and a supporting member in which the first water channel and the second water channel are formed; and a projection member which is coupled to and supported by the supporting member and that lifts the laundry by trapping while the inner tank is rotated, and wherein an inlet of each of the first water channel and the second water channel is formed in the supporting member and the inlet is opened in a tangential direction of the inner tank, so that the washing water flowing in from the side of the outer tank flows out to the inside of the inner tank due to the rotational force being generated when the inner tank is rotated, thereby impacting the laundry which is trapped on the projection member.