It is known that fungal infections, especially candidiasis, are the side effects of broad spectrum antibiotics. As a rule, there prevention is achieved by combining of antibiotics with antifungal agents, but there are other possibilities related to magnetite nanoparticles (NPs). Research aim is to investigate the antifungal properties of magnetite NPs conjugated with ampicillin and stabilized with polyvinylpyrrolidone (PVP) or chitosan. Initial magnetite NPs (5-8 nm) were obtained by the electron-beam technology. They were stabilized with 3% solution of PVP or 1% chitosan solution and conjugated with wide spectrum beta-lactam antibiotic ampicillin (50 mg/ml). Composite NPs were isolated from solutions by magnetic sedimentation. Their hydrodynamic size was determined by laser correlation spectroscopy. Antifungal activity was studied by the standard serial dilutions method using a reference strain of Candida albicans ATCC 10231 and a clinical isolate of Candida albicans. It is shown that in the samples with ampicillin an average hydrodynamic size of particles was 640 nm (with PVP) or 410 nm (with chitosan). Magnetite NPs, stabilized by PVP and loaded with antibiotic, did not inhibit the growth of test cultures of the standard strain Candida albicans ATCC 10231 and clinical Candida isolate. When chitosan was used to stabilize NPs, these particles had antifungal activity with minimal fungistatic concentration within the range of 10-5.5 μg/ml. It did not significantly differ for the standard strain and clinical isolate of Candida albicans. So, there are reasons to believe that the antifungal effect of composite NPs with ampicillin and chitosan is mainly due to chitosan, which itself has antifungal properties. Such pharmacological agent can provide both the usual antibacterial effect of ampicillin and prevent the development of candidiasis that is very profitable for clinic.