A delivery system including a server device (10, 110) and a client device (20, 120) configured to be communicable with each other, wherein: the server device (10, 110) is configured to be able to transmit, to the client device (20, 120), content data in which a piece of content is encoded at an arbitrary one of a plurality of different bit rates; the client device (20, 120) is configured to receive content data transmitted by the server device (10, 110), store the received content data in its storage device and reproduce the content based on the stored content data; and the delivery system comprises: remaining reproduction time acquisition means (25, 130) for acquiring remaining reproduction time that is a period of time during which the content can be reproduced based on a portion of the data stored in the storage device of the client device (20, 120) that has not been reproduced, the remaining reproduction time being obtained by dividing a size of the unreproduced data by a bit rate of the unreproduced data; and bit rate changing means (14, 140) for calculating, according to a predetermined correction amount calculation procedure, a correction amount for correcting the bit rate of the content data transmitted by the server device (10, 110) based on the acquired remaining reproduction time and a preset target value so as to approximate the remaining reproduction time to the target value, and changing the bit rate based on the calculated correction amount, characterized in that the delivery system further comprises reception rate acquisition means for acquiring a reception rate that is an amount of the content data received by the client device (20, 120) from the server device (10, 110) per unit time; and the bit rate changing means (14, 140) is configured to determine an upper limit and a lower limit of a correction amount reducing range based on the acquired reception rate, the acquired remaining reproduction time, and the target value, to calculate the correction amount based on the determined upper limit and the determined lower limit of the correction amount reducing range, and to set the correction amount to zero when a bit rate of content data being transmitted by the server device (10, 110) is within the correction amount reducing range. the server device (10, 110) is configured to be able to transmit, to the client device (20, 120), content data in which a piece of content is encoded at an arbitrary one of a plurality of different bit rates; the client device (20, 120) is configured to receive content data transmitted by the server device (10, 110), store the received content data in its storage device and reproduce the content based on the stored content data; and the delivery system comprises: remaining reproduction time acquisition means (25, 130) for acquiring remaining reproduction time that is a period of time during which the content can be reproduced based on a portion of the data stored in the storage device of the client device (20, 120) that has not been reproduced, the remaining reproduction time being obtained by dividing a size of the unreproduced data by a bit rate of the unreproduced data; and bit rate changing means (14, 140) for calculating, according to a predetermined correction amount calculation procedure, a correction amount for correcting the bit rate of the content data transmitted by the server device (10, 110) based on the acquired remaining reproduction time and a preset target value so as to approximate the remaining reproduction time to the target value, and changing the bit rate based on the calculated correction amount, characterized in that remaining reproduction time acquisition means (25, 130) for acquiring remaining reproduction time that is a period of time during which the content can be reproduced based on a portion of the data stored in the storage device of the client device (20, 120) that has not been reproduced, the remaining reproduction time being obtained by dividing a size of the unreproduced data by a bit rate of the unreproduced data; and bit rate changing means (14, 140) for calculating, according to a predetermined correction amount calculation procedure, a correction amount for correcting the bit rate of the content data transmitted by the server device (10, 110) based on the acquired remaining reproduction time and a preset target value so as to approximate the remaining reproduction time to the target value, and changing the bit rate based on the calculated correction amount, characterized in that the delivery system further comprises reception rate acquisition means for acquiring a reception rate that is an amount of the content data received by the client device (20, 120) from the server device (10, 110) per unit time; and the bit rate changing means (14, 140) is configured to determine an upper limit and a lower limit of a correction amount reducing range based on the acquired reception rate, the acquired remaining reproduction time, and the target value, to calculate the correction amount based on the determined upper limit and the determined lower limit of the correction amount reducing range, and to set the correction amount to zero when a bit rate of content data being transmitted by the server device (10, 110) is within the correction amount reducing range.