A method of controlling a work machine including a working implement with a boom, an arm, and a bucket, includes: acquiring distance data between the bucket and a target excavating topography; determining a target blade tip speed of the bucket based on the distance data; calculating a target boom speed based on the target blade tip speed and at least one of an arm operation amount and a bucket operation amount; calculating a correction amount of the target boom speed based on an integration in time of a distance between the bucket and the target excavating topography; limiting the correction amount based on the distance between the bucket and the target excavating topography; and outputting an instruction for driving a boom cylinder driving the boom based on the target boom speed corrected by the correction amount.