To provide a bottom raisable bed provided with side guards fixed on the bottom without troublesomeness such as pinching a part of the body of a patient or colliding with the other side guard body by one side guard body on the back bottom side moving in the other side guard body direction according to a rise of the back bottom, or an inclining angle increase, in a state where a space between the right and left side guard bodies is so adjusted to have a narrow or no gap, in the case of an intentional operation of raising the back bottom, to securely prevent the patient from falling out in the night when supervising patients is difficult and an adequate treatment or the like is not conducted.

Side guard support members 4 for supporting the side guard bodies are movably provided on the bottom fixing members 15 by move support means. Position detecting means 20L and 20R of the side guard support members 4 are provided on the bottom fixing members 15. In the case of occurrence of the narrow distance between the side guard main bodies, a control means of a bottom raising mechanism detects the state to render the raising operation of the back bottom invalid.