Described are novel chimeric anti-human immunodeficiency virus (HIV) antibodies which comprise a constant region derived from human antibody and variable region derived from mouse monoclonal antibody, gene fragments coding for the variable region the H and L chain of chimeric anti-HIV antibodies which are effective for expression of chimeric anti-HIV antibodies having an HIV-neutralizing activity, a transformant where such gene fragments are incorporated, chimeric anti-HIV antibodies expressed therefrom and a process for their preparation. The chimeric anti-HIV antibodies of the present invention show anti-HIV neutralizing activity and are useful for the diagnosis, treatment and prevention of acquired immunodeficiency syndrome (AIDS) caused by HIV without side effects such as anaphylactic shock or serum sickness.