An image pickup apparatus that is configured to vary its optical properties by moving a part of lenses of an objective lens comprised in the apparatus, the apparatus further comprising: a solid-state image pickup device unit that is arranged at a rear-end section and that subjects a subject image to photoelectric conversion; a fixed lens frame that is adapted to retain the objective lens that is disposed to the front of the solid-state image pickup device unit; a movable lens frame that is adapted to retain the part of lenses that moves along a photographing optical axis inside the lens frame; and an actuator that is configured to move the movable lens frame forward and backward, and that includes a rod-shaped rigid member having one end connected to the movable lens frame through a connection rod into which the one end of the rigid member is screwed, and a shape memory alloy that is coupled to the rigid member, wherein a temperature of the shape memory alloy being varied to a predetermined temperature by an electric current that is applied from an external power source so as to control expanding and contracting of the shape memory alloy, characterized by a first clearance formed in a circumferential direction of the movable lens frame between the movable lens frame and the fixed lens frame, an outer diameter of the movable lens frame being smaller than an inner diameter of the fixed lens frame; a guide pipe that is fixed to the fixed lens frame and into which the rod-shaped rigid member is insertedly fitted to be movable forward and backwards and that rectilinearly guides the rigid member in a photographing optical axis direction of the solid-state image pickup device unit; a hole portion that is formed at the fixed lens frame and has a hole diameter larger than an outer diameter of the guide pipe, and into which the guide pipe is inserted; a second clearance formed in a circumferential direction of the guide pipe between the guide pipe and the fixed lens frame; and a fixing member that is adapted to fix a position of an axis of the guide pipe in the fixed lens frame so that the position of the axis of the guide pipe is variably set within the second clearance. a solid-state image pickup device unit that is arranged at a rear-end section and that subjects a subject image to photoelectric conversion; a fixed lens frame that is adapted to retain the objective lens that is disposed to the front of the solid-state image pickup device unit; a movable lens frame that is adapted to retain the part of lenses that moves along a photographing optical axis inside the lens frame; and an actuator that is configured to move the movable lens frame forward and backward, and that includes a rod-shaped rigid member having one end connected to the movable lens frame through a connection rod into which the one end of the rigid member is screwed, and a shape memory alloy that is coupled to the rigid member, wherein a temperature of the shape memory alloy being varied to a predetermined temperature by an electric current that is applied from an external power source so as to control expanding and contracting of the shape memory alloy, a first clearance formed in a circumferential direction of the movable lens frame between the movable lens frame and the fixed lens frame, an outer diameter of the movable lens frame being smaller than an inner diameter of the fixed lens frame; a guide pipe that is fixed to the fixed lens frame and into which the rod-shaped rigid member is insertedly fitted to be movable forward and backwards and that rectilinearly guides the rigid member in a photographing optical axis direction of the solid-state image pickup device unit; a hole portion that is formed at the fixed lens frame and has a hole diameter larger than an outer diameter of the guide pipe, and into which the guide pipe is inserted; a second clearance formed in a circumferential direction of the guide pipe between the guide pipe and the fixed lens frame; and a fixing member that is adapted to fix a position of an axis of the guide pipe in the fixed lens frame so that the position of the axis of the guide pipe is variably set within the second clearance.