Control system for loading machine, loading machine, and control method for loading machine

A control system for a loading machine having a working machine including a bucket is provided with a control device. The control device detects a first surface of an excavated object excavated by the bucket in the excavation operation; calculating, based on the detection data of the first surface, an in-excavation cargo loading angle representing an angle of the first surface with respect to a horizontal plane; and the weight of the excavated object is calculated based on the cargo carrying angle during excavation. 具有包含铲斗的作业机的装载机械的控制系统具备控制装置。控制装置对在挖掘作业中通过铲斗挖掘出的挖掘物的第一表面进行检测；并且基于第一表面的检测数据，计算表示第一表面相对于水平面的角度的挖掘中载货角；并且基于挖掘中载货角推算挖掘物的重量。