Saurashtra scored 477 in the first innings and took a vital 178-run lead over Punjab by dismissing them for 299.
In the second essay, the hosts were dismissed for 170, setting Punjab a victory target of 349 to win the semi-final match.
However, the visitors were skittled out for 119. Saurashtra took just 21 overs to clean up the eight remaining wickets on the fifth and final day this morning.
Joshi, who scalped four wickets in the first innings, again proved to be the wrecker-in-chief, taking five wickets conceding only 43 runs. He was ably supported by Dharmendra Jadeja (3/25) and Jaydev Unadkat (2/30).
Resuming the day at 45 for 2, Punjab batsmen failed to negotiate Joshi and left-arm leg spinner Dharmendra Jadeja. The visitors surrendered meekly and the entire team was bundled out for a paltry 119 off 40 overs.
Overnight batsmen Mandeep Singh was the first man to be dismissed, outclassed by a beauty from Joshi, and then the rest of the batting order collapsed like a house of cards.
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Joshi and Jadeja were simply unplayable on a track that started assisting bowlers from the final session of the fourth day.
Mandeep (33) was the highest scorer for his team in the second essay as half a dozen Punjab batsmen failed to even reach the double digit mark. Ravi Inder Singh contributed 25 runs.
Joshi, who finished the match with 9 for 102 runs, was declared man of the match.
Saurashtra's earlier avatars Navanagar and WISCA (Western India State Cricket Association) have played in the final of the prestigious domestic tournament.
In 2006, Saurashtra had won the Ranji Plate division title by beating the Ajay Jadeja-led Rajasthan here.
Brief scores: Saurashtra 477 and 170 beat Punjab by 229 runs. Punjab 299 and 119 (Mandeep Singh 33, Ravi Inder Singh 25, Vishal Joshi 5-43, Dharmendra Jadeja 3-25 and Jaydev Unadkat 2-30).