A knee airbag for a vehicle including a steering column, the knee airbag comprising: a lower crash pad having a panel shape for blocking the steering column to prevent exposure of the steering column to an indoor space of the vehicle, and including a housing unit having recesses dented toward the steering column such that the housing unit is spaced apart from the steering column by a designated distance; and an airbag module including an inflator and a cushion and contained in the housing unit of the lower crash pad configured to deploy the cushion toward a driver's knee outside the lower crash pad when the cushion is deployed by explosion of the inflator, characterized in that: the knee airbag further comprises a stopper having a frame shape for being coupled to a lower portion of the steering column and tilted up and down together with tilt-up and down of the steering column, wherein the housing unit of the lower crash pad is supported by the stopper when the housing unit retreats to an upper portion or a front portion of the vehicle by deployment pressure when the cushion is deployed, wherein the stopper includes: a first part having a panel shape that extends from a point of the stopper for being coupled to the steering column to a rear portion of the vehicle; and a second part having a panel shape that extends from the point of the stopper for being coupled to the steering column to a lower portion of the vehicle, wherein the first part and the second part of the stopper are spaced apart from the housing unit of the lower crash pad by a designated distance. a lower crash pad having a panel shape for blocking the steering column to prevent exposure of the steering column to an indoor space of the vehicle, and including a housing unit having recesses dented toward the steering column such that the housing unit is spaced apart from the steering column by a designated distance; and an airbag module including an inflator and a cushion and contained in the housing unit of the lower crash pad configured to deploy the cushion toward a driver's knee outside the lower crash pad when the cushion is deployed by explosion of the inflator, characterized in that: the knee airbag further comprises a stopper having a frame shape for being coupled to a lower portion of the steering column and tilted up and down together with tilt-up and down of the steering column, wherein the housing unit of the lower crash pad is supported by the stopper when the housing unit retreats to an upper portion or a front portion of the vehicle by deployment pressure when the cushion is deployed, wherein the stopper includes: a first part having a panel shape that extends from a point of the stopper for being coupled to the steering column to a rear portion of the vehicle; and a second part having a panel shape that extends from the point of the stopper for being coupled to the steering column to a lower portion of the vehicle, wherein the first part and the second part of the stopper are spaced apart from the housing unit of the lower crash pad by a designated distance. the knee airbag further comprises a stopper having a frame shape for being coupled to a lower portion of the steering column and tilted up and down together with tilt-up and down of the steering column, wherein the housing unit of the lower crash pad is supported by the stopper when the housing unit retreats to an upper portion or a front portion of the vehicle by deployment pressure when the cushion is deployed, wherein the stopper includes: a first part having a panel shape that extends from a point of the stopper for being coupled to the steering column to a rear portion of the vehicle; and a second part having a panel shape that extends from the point of the stopper for being coupled to the steering column to a lower portion of the vehicle, a first part having a panel shape that extends from a point of the stopper for being coupled to the steering column to a rear portion of the vehicle; and a second part having a panel shape that extends from the point of the stopper for being coupled to the steering column to a lower portion of the vehicle, wherein the first part and the second part of the stopper are spaced apart from the housing unit of the lower crash pad by a designated distance.