In controlling a mesh-body worm robot which can do peristaltic motion to progress, slip reduction is important especially in turning, in which body angle always tends to turn back after each attempt to make a turn. In our previous work, a mathematical model was constructed to study these mesh-body worm robots and slip reduction controls in straight-line motion were developed analytically. However, rules behind turning motion are more complicated to analyze than straight-line motion. Therefore, in this work, we developed a new method to numerically search all possible controls for slip reduction and return the optimum one. As a result, the new control waveform sufficiently eliminates the motion slip in all turning biases.