A work machine comprising: a work implement having a bucket, an arm, and a boom; a plurality of hydraulic actuators (5,6,7) that drive the work implement; operation devices (45,46) that instruct the hydraulic actuators (5,6,7) on operations; and a controller configured to control the hydraulic actuators (5,6,7) such that, during operations of the operation devices (45,46), an operating range of the work implement is limited on a predetermined first target surface and to an area superior to the first target surface, characterized in that the controller includes: a storage section that stores position information of a current landform; a bucket position calculation section that calculates a position of a claw tip of the bucket; an estimated excavation volume calculation section that calculates an estimated excavation volume (Va) defined by a first position that assumes the position of the claw tip of the bucket calculated by the bucket position calculation section at an excavation start, a second position that assumes the position of the claw tip of the bucket at an excavation end set in advance, the current landform, the first target surface, and a width of the bucket; and a target surface generation section that generates, when the estimated excavation volume (Va) exceeds a limit volume (Vb) set in advance, a second target surface at a position superior to the first target surface, the target surface generation section generates the second target surface at a position at which the excavation volume defined by the first position, the second position, the current landform, the second target surface, and the width of the bucket is closer to the limit volume (Vb), and when the second target surface is generated, the controller controls the hydraulic actuators (5,6,7) such that the operating range of the work implement is limited on the second target surface and to an area superior to the second target surface. a work implement having a bucket, an arm, and a boom; a plurality of hydraulic actuators (5,6,7) that drive the work implement; operation devices (45,46) that instruct the hydraulic actuators (5,6,7) on operations; and a controller configured to control the hydraulic actuators (5,6,7) such that, during operations of the operation devices (45,46), an operating range of the work implement is limited on a predetermined first target surface and to an area superior to the first target surface, characterized in that the controller includes: a storage section that stores position information of a current landform; a bucket position calculation section that calculates a position of a claw tip of the bucket; an estimated excavation volume calculation section that calculates an estimated excavation volume (Va) defined by a first position that assumes the position of the claw tip of the bucket calculated by the bucket position calculation section at an excavation start, a second position that assumes the position of the claw tip of the bucket at an excavation end set in advance, the current landform, the first target surface, and a width of the bucket; and a target surface generation section that generates, when the estimated excavation volume (Va) exceeds a limit volume (Vb) set in advance, a second target surface at a position superior to the first target surface, the target surface generation section generates the second target surface at a position at which the excavation volume defined by the first position, the second position, the current landform, the second target surface, and the width of the bucket is closer to the limit volume (Vb), and when the second target surface is generated, the controller controls the hydraulic actuators (5,6,7) such that the operating range of the work implement is limited on the second target surface and to an area superior to the second target surface. a storage section that stores position information of a current landform; a bucket position calculation section that calculates a position of a claw tip of the bucket; an estimated excavation volume calculation section that calculates an estimated excavation volume (Va) defined by a first position that assumes the position of the claw tip of the bucket calculated by the bucket position calculation section at an excavation start, a second position that assumes the position of the claw tip of the bucket at an excavation end set in advance, the current landform, the first target surface, and a width of the bucket; and a target surface generation section that generates, when the estimated excavation volume (Va) exceeds a limit volume (Vb) set in advance, a second target surface at a position superior to the first target surface, the target surface generation section generates the second target surface at a position at which the excavation volume defined by the first position, the second position, the current landform, the second target surface, and the width of the bucket is closer to the limit volume (Vb), and when the second target surface is generated, the controller controls the hydraulic actuators (5,6,7) such that the operating range of the work implement is limited on the second target surface and to an area superior to the second target surface.