This study aimed to elucidate the effects of nudging healthy food choices in cafeteria ticket vending machines on guiding peoples’ preferences in a healthier direction, and to consider the surrounding ethical issues. This study was conducted for 3 weeks in the city hall cafeteria. The salad button was placed at the bottom of the ticket vending machine during the control period. During test 1, the salad button was positioned around eye level to nudge preferences. During test 2, the purpose of this nudging was disclosed to the participants in order to explore relevant ethical issues. A survey was conducted to understand participant awareness of menu selection and to evaluate the acceptance of nudging before and after its disclosure. The number of salad purchases during test 2 increased significantly compared to that during the control period (0.6 vs 1.4 vs 3.2/total sales number, p=0.041). The percentages of “Don’t care about being nudged” attitudes during tests 1 and 2 were 73.3% and 64.0%, respectively (p=0.187). Our results suggest that nudging would increase healthy food choices, thereby guiding people to a healthier direction. Additionally, disclosing the purpose of nudging resulted in behavioral changes while also maintaining autonomous decision-making.