Seikan Ishigai found the inner development law based on the theorem that there exists contradiction between power and control in the labour process. Ishigai explains the theorem as follows. Generally speaking, power and control are independent notions respectively and in the active process of technology there exist no power without control and no control without power. These necessarily rest upon one another. We can express that a pair which consists of power and control is a pair of terms that contradict but unify one another. So a pair which consists of power and control has two fold of characters. When human beings in the active technology make all the artificial things move, they add mechanical labour. We explain two fold of characters of power and control not as one of many factors but as essential factor in the active technology, therefore the labour means has power aspect and control aspect, regulated by the theorem, and continues to separate unlimitedly. I trace inner development of shipping technology according to the above theorem. Shipping technology begins with swimming. In swimming propulsion power and direction control are covered by hands and feet movements, after that both are replaced by the labour means, that is, propulsion and direction function is replaced by scull with body conditions of shipping shape. Then scull is separated into oar that covers propulsion power and into paddle that covers direction control. The function of propulsion power and paddle control increases, and at the end of the function paddle is replaced by hinge rudder in parallel with oar replaced by sail. Futhermore, in accordance with social demand the function increases and at the end of the function, then sail is replaced by propeller and hinge rudder by reunited rudder. Propulsion power and direction control system improves new quality. In this case the basic factor of shipping exists in two fold characters of the labour, that is, contradiction exists between power and control in the labour process, so rudder and propeller unite again.