diff --git a/packages/vite/src/node/plugins/css.ts b/packages/vite/src/node/plugins/css.ts
index 26ba17c192f84e..dc2964ab57ca8e 100644
--- a/packages/vite/src/node/plugins/css.ts
+++ b/packages/vite/src/node/plugins/css.ts
@@ -594,7 +594,9 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
 
         const toRelative = (filename: string) => {
           // relative base + extracted CSS
-          const relativePath = path.posix.relative(cssAssetDirname!, filename)
+          const relativePath = normalizePath(
+            path.relative(cssAssetDirname!, filename),
+          )
           return relativePath[0] === '.' ? relativePath : './' + relativePath
         }
 
@@ -615,9 +617,8 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
         })
         // resolve public URL from CSS paths
         if (encodedPublicUrls) {
-          const relativePathToPublicFromCSS = path.posix.relative(
-            cssAssetDirname!,
-            '',
+          const relativePathToPublicFromCSS = normalizePath(
+            path.relative(cssAssetDirname!, ''),
           )
           chunkCSS = chunkCSS.replace(publicAssetUrlRE, (_, hash) => {
             const publicUrl = publicAssetUrlMap.get(hash)!.slice(1)
diff --git a/packages/vite/src/node/plugins/html.ts b/packages/vite/src/node/plugins/html.ts
index b7109debc3863a..da548c4f7cf4ba 100644
--- a/packages/vite/src/node/plugins/html.ts
+++ b/packages/vite/src/node/plugins/html.ts
@@ -330,7 +330,7 @@ export function buildHtmlPlugin(config: ResolvedConfig): Plugin {
     async transform(html, id) {
       if (id.endsWith('.html')) {
         id = normalizePath(id)
-        const relativeUrlPath = path.posix.relative(config.root, id)
+        const relativeUrlPath = normalizePath(path.relative(config.root, id))
         const publicPath = `/${relativeUrlPath}`
         const publicBase = getBaseInHTML(relativeUrlPath, config)
 
@@ -776,7 +776,9 @@ export function buildHtmlPlugin(config: ResolvedConfig): Plugin {
       }
 
       for (const [normalizedId, html] of processedHtml) {
-        const relativeUrlPath = path.posix.relative(config.root, normalizedId)
+        const relativeUrlPath = normalizePath(
+          path.relative(config.root, normalizedId),
+        )
         const assetsBase = getBaseInHTML(relativeUrlPath, config)
         const toOutputFilePath = (
           filename: string,