Due to the fear of COVID-19, there have been an increasing number of people who are willing to pay for health food to strengthen the immune system. Therefore, the current study aims to examine how the fear of COVID-19 influences the intentions of people who purchase health foods. We used Theory of Planned Behavior (TPB) as the theoretical background to explain the relationships among the constructs. The study was conducted using a quantitative research method with a sample of 294 participants collected in Taiwan. Structural Equation Modeling (SEM) was utilized to evaluate the fit of the entire research model with the observation data and Path analysis was used for hypothesis testing, which indicates the strength of the relationships between the variables. The research findings show that the variable of Fear of COVID-19 can predict other variables such as Attitudes, Subjective Norms, Perceived Behavioral Control and Purchase Intention in the TPB. The research findings suggest that COVID-19 affects people's willingness to buy health food. People are seeking to improve their immunity and hope to keep healthy to fight the virus. People's fear of the numbers of infected cases and deaths increase drastically due to the outbreak of COVID-19, which makes people pay more attention to health, and may have changed people's willingness to buying health food.