It is intended to provide a foreign protein free from any expression inducer and a process for producing the same. Namely, a process for producing a foreign protein involving the step of proliferating a recombinant Escherichia coli, which expresses the foreign protein under the control by a promoter capable of inducing the expression due to the temperature shift, by arbitrarily culturing at a low temperature and then culturing the strain at a high temperature in the absence of an expression inducer to thereby allow the expression of the foreign protein, or the step of culturing the above Escherichia coli strain at a high temperature and thus effecting the proliferation of the cells and the expression of the foreign protein at the same time; and a foreign protein free from any expression inducer which is obtained by this process. Particular examples of such foreign proteins include main tick allergens, Actinogacillus pleuropneumoniae-origin secretory macrophage toxin and a protective antigen against Erysipelothrix rhusiopathiae-infection.