A heterologous protein free from an inducer and a method for producing said protein are provided. A method for producing a heterologous protein which comprises the step of optionally culturing at low temperature recombinant E. coli cells expressing a heterologous protein under control of a promoter capable of inducing expression through temperature shift and then culturing at high temperature said recombinant E. coli cells in the absence of an inducer to thereby allow for expression of said heterologous protein, or the step of culturing at high temperature said recombinant E. coli cells to thereby simultaneously allow for both cell proliferation and expression of said heterologous protein, and the heterologous protein obtained by said method that is free from an inducer. Such heterologous protein may include a major mite allergen, a secretary macrophage toxin from Actinobacillus pleuropneumoniae and a surface protective antigen (SpaA) of Erysipelothrix rhusiopathiae.