A travel control method using an ambient detection sensor configured to detect information on a lane boundary line of a lane around a subject vehicle as real boundary line information from an actual environment around the subject vehicle, the travel control method comprising: detecting the real boundary line information on a basis of detection results by the ambient detection sensor; determining whether or not a portion that coincides with the real boundary line information exists in map boundary line information, the map boundary line information being information on the lane boundary line of the lane included in map information; integrating the real boundary line information and the map boundary line information to generate integrated boundary line information when the portion that coincides with the real boundary line information exists in the map boundary line information, wherein a coincident portion with the real boundary line information is detected in the map boundary line information, and the real boundary line information is complemented with information on a portion other than the coincident portion in the map boundary line information thereby to generate the integrated boundary line information; outputting the integrated boundary line information; and controlling travel of the subject vehicle on a basis of the output integrated boundary line information; characterized in that a degree of reliability of the real boundary line information detected by the ambient detection sensor is determined; when the degree of reliability of the real boundary line information is not less than a predetermined value, a range of the real boundary line information before being integrated with the map boundary line information is expanded as compared with a case in which the degree of reliability of the real boundary line information is less than the predetermined value. detecting the real boundary line information on a basis of detection results by the ambient detection sensor; determining whether or not a portion that coincides with the real boundary line information exists in map boundary line information, the map boundary line information being information on the lane boundary line of the lane included in map information; integrating the real boundary line information and the map boundary line information to generate integrated boundary line information when the portion that coincides with the real boundary line information exists in the map boundary line information, wherein a coincident portion with the real boundary line information is detected in the map boundary line information, and the real boundary line information is complemented with information on a portion other than the coincident portion in the map boundary line information thereby to generate the integrated boundary line information; outputting the integrated boundary line information; and controlling travel of the subject vehicle on a basis of the output integrated boundary line information; characterized in that a degree of reliability of the real boundary line information detected by the ambient detection sensor is determined; when the degree of reliability of the real boundary line information is not less than a predetermined value, a range of the real boundary line information before being integrated with the map boundary line information is expanded as compared with a case in which the degree of reliability of the real boundary line information is less than the predetermined value.