Objective: This study investigated the measurement interval in the ultrasonographic gastric emptying test for patients with functional dyspepsia (FD) and the correlation between gastric emptying and the findings of various questionnaires. Methods: In total, 119 patients (59 patients with FD and 60 healthy controls) were recruited from July 2018 to June 2020. Gastric volume (GV) and gastric emptying half-time (T1/2) were measured by ultrasonography at fasting and again at 0, 5, 10, 15, 30, 45, 60, 90, and 120 min after meals (apple juice, 500 mL, 224 kcal), and the average half-time (average T1/2) was calculated. Questionnaires on food retention (FRQ), phlegm pattern e (PPQ), cold and heat (CHQ), deficiency and excess (DEQ), and spleen-qi deficiency (SQDQ), stomach qi deficiency pattern (SSDQ), visual analogue scale (VAS), and Nepean dyspepsia index-Korean version (NDI-K) were completed by all participants. The differences in GV and T1/2 were analyzed in participants whose maximal GV occurred at 0 min versus after 0 min. The correlation of the average T1/2 with the questionnaire scores was also analyzed after excluding erroneous data. Results: Patients with FD who took a certain amount of time to reach maximal GV after meals had a greater gastric volume up to about 30 minutes after meals, and the PPQ, DEQ, and NDI-K scores, especially for upper gastrointestinal symptoms and general weakness-related symptoms, showed statistically significant correlations with average T1/2. Conclusions: Ultrasonography can be a quantitative evaluation tool for FD. However, further studies on measurement methods based on FD physiopathology are required.