An inference device is disclosed including a rule base including a graph data structure corresponding to a table formed from columns, each column corresponding to a symbol, and one or more rows including cells, each cell arranged in a position of a column and storing a value for forming a logical expression by applying to each symbol corresponding to a column where the cell is located, the graph data structure including a root node and sequences of nodes connected in series, each sequence of nodes corresponding to a row and each node corresponding to a cell. An end-node of each sequence nodes is connected to the root node, the nodes can be scanned in order following pointers from the root node, each row represents a rule in which logical expressions are arranged on the left side as a logical conjunction and logical expressions are arranged on the right side.