1. A reference pattern generating device including: a feature analyzer, responsive to a speech signal representative of an input pattern, for producing a time sequence of feature vectors representative of said input pattern; a table storing a plurality of code vectors of known vocabulary and a plurality of feature codes respectively corresponding to said plurality of code vectors; converting means, connected to said feature analyzer and said table, for converting a plurality of time sequences of feature vectors to a plurality of time sequences of feature codes with reference to said table, said plurality of time sequences of feature vectors being produced in response to a plurality of speech signals; and first forming means for forming, in response to said plurality of time sequences of feature codes, a state transition probability in a state transition network and a probability distribution of occurrence of the feature codes in each state in said state transition network; where the improvement comprises: function generating means, connected to said table and said first forming means, for generating an approximate continuous probability density function, said approximate continuous probability density function approximating said probability distribution of occurrence of the feature codes in each state in said state transition network, said code vectors being used as parameters in said approximate continuous probability density function; and second forming means, connected to said first forming means and said function generating means, for forming as a reference pattern for said plurality of speech signals a combination of said state transition probability distribution and said approximate continuous probability density function.