The aim of this work was to characterize an antibody response to β-glucan (BG), a major component of the fungal cell wall, at each isotype in human sera. The titer and reactivity of the anti-human BG antibody were examined using enzyme-linked immunosorbant assay plates coated with Candida soluble cell wall β-glucan as a standard antigen. The antibody was detected using anti-human immunoglobulin (Ig) G, IgM, and IgA. Its major class was IgG in all subjects. The antibody titer varied significantly. The anti-BG antibody showed greater reactivity to β-glucans derived from pathogenic fungi than monoglycosyl-branched β-glucans derived from mycelia culture medium. In addition, it was suggested that the anti-BG IgM antibody was bound relatively strongly to the β1,3-glucan backbone and the anti-BG IgG antibody to β1,6-glucan. The anti-BG antibody plays a variety of roles, according to class, in the host's response to fungi. We propose a new index of human response to β-glucan that effects the understanding of the response to β-glucan in humans.