1. An information processing apparatus for detecting a predetermined pattern in an input image by a process employing a hierarchical neural network in which a plurality of detection layers and integration layers are arranged alternately, the detection layer detecting and outputting one or more feature amounts from the output of the integration layer at the former stage and the integration layer integrating the outputted features from the detection layer at the former stage and outputting the result of integration, comprising: output value computation means for computing an output value of neuron within an objective layer, using an output value of neuron within a former layer of the objective layer and a weight coefficient between the objective layer and the former layer, sequentially by setting each layer as the objective layer; first storage control means for storing data of the output value, which is greater than or equal to a predetermined value, in a memory by referring to the output value of each neuron within the detection layer computed by said output value computation means; second storage control means for storing data of the output value of each neuron within the integration layer computed by said output value computation means, in the memory; and supply means for supplying the data of the output value of neuron within the former layer of the objective layer to said output value computation means by reading the data of the output value from the memory and supplying the data having a predetermined value instead of the data of the output value of neuron not stored in the memory.