1. A landing-control device for an aircraft, comprising: a detecting unit detecting at least a relative altitude form a landing surface to the aircraft; a parameter-generating unit constructed by a neural network that takes a detection value detected by the detecting unit as its input and outputs a landing-control parameter of the aircraft, the neural network having a feedback loop wherein an output of a first node of the neural network is input to a second node different from the first node; and a controlling unit controlling the aircraft based on the landing-control parameter output from the parameter-generating unit.