An underwater moving apparatus, comprising: a body; a propelling device installed on a rear side of the body; a thruster unit including an up and down directional thruster (52, 54) and a left and right directional thruster ((56, 58) installed at the body and a plurality of leg units positioned at both side portions of the body and including a multi-joint module; the underwater moving apparatus further comprising: at least one arm unit positioned at a front side of the body and including a multi-joint module and a tail wing unit positioned at a front side of the propelling device; wherein the body has a cross section in a forward and rearward direction having a circular or elliptical shape, and the body has a streamlined shape in which a cross section of a front side of the body is broad, and a cross section of a rear side is narrow, characterized in that the multi-joint module (100;200) includes: a rotating shaft member coupled to the body to be rotatable about a first rotating axis extended in an outward direction of the body; a joint member (120;220) coupled to one end portion of the rotating shaft member to be rotatable about a second rotating axis which is vertical to the first rotating axis; a first frame member (130;230) coupled to one end portion of the joint member to be rotatable about a third rotating axis which is vertical to the first rotating axis and the second rotating axis; and a second frame member (140;240) coupled to one end portion of the first frame member to be rotatable about a fourth rotating axis which is in parallel to the third rotating axis. a body; a propelling device installed on a rear side of the body; a thruster unit including an up and down directional thruster (52, 54) and a left and right directional thruster ((56, 58) installed at the body and a plurality of leg units positioned at both side portions of the body and including a multi-joint module; the underwater moving apparatus further comprising: at least one arm unit positioned at a front side of the body and including a multi-joint module and a tail wing unit positioned at a front side of the propelling device; wherein the body has a cross section in a forward and rearward direction having a circular or elliptical shape, and the body has a streamlined shape in which a cross section of a front side of the body is broad, and a cross section of a rear side is narrow, characterized in that the multi-joint module (100;200) includes: a rotating shaft member coupled to the body to be rotatable about a first rotating axis extended in an outward direction of the body; a joint member (120;220) coupled to one end portion of the rotating shaft member to be rotatable about a second rotating axis which is vertical to the first rotating axis; a first frame member (130;230) coupled to one end portion of the joint member to be rotatable about a third rotating axis which is vertical to the first rotating axis and the second rotating axis; and a second frame member (140;240) coupled to one end portion of the first frame member to be rotatable about a fourth rotating axis which is in parallel to the third rotating axis. at least one arm unit positioned at a front side of the body and including a multi-joint module and a tail wing unit positioned at a front side of the propelling device; wherein the body has a cross section in a forward and rearward direction having a circular or elliptical shape, and the body has a streamlined shape in which a cross section of a front side of the body is broad, and a cross section of a rear side is narrow, characterized in that the multi-joint module (100;200) includes: a rotating shaft member coupled to the body to be rotatable about a first rotating axis extended in an outward direction of the body; a joint member (120;220) coupled to one end portion of the rotating shaft member to be rotatable about a second rotating axis which is vertical to the first rotating axis; a first frame member (130;230) coupled to one end portion of the joint member to be rotatable about a third rotating axis which is vertical to the first rotating axis and the second rotating axis; and a second frame member (140;240) coupled to one end portion of the first frame member to be rotatable about a fourth rotating axis which is in parallel to the third rotating axis. a rotating shaft member coupled to the body to be rotatable about a first rotating axis extended in an outward direction of the body; a joint member (120;220) coupled to one end portion of the rotating shaft member to be rotatable about a second rotating axis which is vertical to the first rotating axis; a first frame member (130;230) coupled to one end portion of the joint member to be rotatable about a third rotating axis which is vertical to the first rotating axis and the second rotating axis; and a second frame member (140;240) coupled to one end portion of the first frame member to be rotatable about a fourth rotating axis which is in parallel to the third rotating axis.