Objective To elucidate the time‐course changes of swallowing function in amyotrophic lateral sclerosis (ALS) by videomanofluorometry. Study Design Videomanofluorometry was conducted on 21 patients with ALS, who were divided into five groups according to type of disease and according to the length of time following the appearance of bulbar symptoms. Methods Videomanofluorometry, which is videofluoroscopic and manometric study conducted simultaneously, was performed on patients in the five groups, and swallowing function in each group was evaluated. Some of the patients were followed up by videomanofluorometry performed several times, and their swallowing function changes over time were investigated. Results A decrease of swallowing pressure first appeared in the oropharynx, then the hypopharynx became involved. Oropharyngeal swallowing pressure had already decreased to approximately 50 mm Hg within 6 months after the appearance of bulbar symptoms; however, hypopharyngeal swallowing pressure was relatively maintained until 1 year after the onset of bulbar symptoms. Most of the patients with ALS maintained normal upper esophageal sphincter relaxation, but upper esophageal sphincter spasm was seen in some patients with ALS. Aspiration was seen in eight cases, five of which showed upper esophageal sphincter spasm. Conclusions Patients with ALS gradually face the danger of aspiration as decreases of oropharyngeal and hypopharyngeal swallowing pressure progress. Upper esophageal sphincter spasm occurs in some patients with ALS, and it is an important cause of aspiration. Both videofluoroscopic and manometric evaluation are necessary to assess these conditions, and they are quite useful for follow‐up of swallowing function in patients with ALS.