A speaker unit adapted to be mounted in an opening section formed in a mounting part, the speaker unit comprising: a cabinet section having an outer peripheral side surface and a bottom surface; a speaker face provided on the bottom surface of the cabinet section; a provisionally fastening mechanism constructed to provisionally fasten the speaker unit with at least a part of the cabinet section inserted in the opening section from a face side of the mounting part; and a flange portion projecting radially outward from an outer peripheral edge of the bottom surface of the cabinet section, wherein said provisionally fastening mechanism includes a provisionally fastening member formed of a resilient material and mounted to the outer peripheral side surface of the cabinet section, said provisionally fastening member including: an engaging section engageable with an inner peripheral edge portion of the opening section on a reverse side of the mounting part to thereby place the speaker unit in a provisionally fastened state; and an operating section exposed to the face side of the mounting part in the provisionally fastened state, wherein the speaker unit further comprises a fixation mechanism for fully fastening the speaker unit provisionally fastened in the opening section by said provisionally fastening mechanism, wherein the speaker unit is configured to define a gap (X, 7a) between the face side surface of the mounting part and the flange portion in the provisionally fastened state to thereby expose said operating section within the gap (X, 7a) behind the flange portion, wherein said provisionally fastening member is configured to resiliently deform, in response to said operating section being operated with a finger through the gap (X, 7a), so that the provisionally fastened state is canceled by engagement of said engaging section with the inner peripheral edge portion of the opening section being canceled, characterized in that said provisionally fastening member integrally has: a mounting section fixed to the outer peripheral side surface of the cabinet section; a slanting section extending obliquely downward from the mounting section toward a radially outward end of the cabinet section and toward the bottom surface; the engaging section extending radially inward from a distal end of said slanting section; and said operating section extending from a distal end of said engaging section toward the bottom surface of the cabinet section and wherein said gap (X, 7a) is closed as the speaker unit is fully fastened by the fixation mechanism. a cabinet section having an outer peripheral side surface and a bottom surface; a speaker face provided on the bottom surface of the cabinet section; a provisionally fastening mechanism constructed to provisionally fasten the speaker unit with at least a part of the cabinet section inserted in the opening section from a face side of the mounting part; and a flange portion projecting radially outward from an outer peripheral edge of the bottom surface of the cabinet section, wherein said provisionally fastening mechanism includes a provisionally fastening member formed of a resilient material and mounted to the outer peripheral side surface of the cabinet section, said provisionally fastening member including: an engaging section engageable with an inner peripheral edge portion of the opening section on a reverse side of the mounting part to thereby place the speaker unit in a provisionally fastened state; and an operating section exposed to the face side of the mounting part in the provisionally fastened state, wherein the speaker unit further comprises a fixation mechanism for fully fastening the speaker unit provisionally fastened in the opening section by said provisionally fastening mechanism, an engaging section engageable with an inner peripheral edge portion of the opening section on a reverse side of the mounting part to thereby place the speaker unit in a provisionally fastened state; and an operating section exposed to the face side of the mounting part in the provisionally fastened state, wherein the speaker unit further comprises a fixation mechanism for fully fastening the speaker unit provisionally fastened in the opening section by said provisionally fastening mechanism, wherein the speaker unit is configured to define a gap (X, 7a) between the face side surface of the mounting part and the flange portion in the provisionally fastened state to thereby expose said operating section within the gap (X, 7a) behind the flange portion, wherein said provisionally fastening member is configured to resiliently deform, in response to said operating section being operated with a finger through the gap (X, 7a), so that the provisionally fastened state is canceled by engagement of said engaging section with the inner peripheral edge portion of the opening section being canceled, characterized in that said provisionally fastening member integrally has: a mounting section fixed to the outer peripheral side surface of the cabinet section; a slanting section extending obliquely downward from the mounting section toward a radially outward end of the cabinet section and toward the bottom surface; the engaging section extending radially inward from a distal end of said slanting section; and said operating section extending from a distal end of said engaging section toward the bottom surface of the cabinet section and wherein said gap (X, 7a) is closed as the speaker unit is fully fastened by the fixation mechanism.